[PATCH v2] eeprom/optoe: driver to read/write SFP/QSFP/CMIS EEPROMS

[Don Bollinger]

optoe is an i2c based driver that supports read/write access to all
the pages (tables) of MSA standard SFP and similar devices (conforming
to the SFF-8472 spec), MSA standard QSFP and similar devices (conforming
to the SFF-8636 spec) and CMIS and similar devices (conforming to the
Common Management Interface Specfication).

These devices provide identification, operational status and control
registers via an EEPROM model.  These devices support one or 3 fixed pages
(128 bytes) of data, and one page that is selected via a page register on
the first fixed page.  Thus the driver's main task is to map these pages
onto a simple linear address space for user space management applications.
See the driver code for a detailed layout.

Several variants and predecessors of this driver exist outside the kernel
tree.  Some of them don't support pages at all, only accessing the first
256 bytes of EEPROM.  None of them handle all three specifications, none
of them support pages beyond page 3.  This is a problem since critical
monitoring data on CMIS devices is on page 0x11.  Some of them don't
support pages at all, only accessing the first 256 bytes of data.  optoe
supports the full architected 256 page address space of these devices.
optoe is currently in production on multiple platforms running SONiC
(Microsoft's Software for Open Networking in the Cloud) and ONL (Open
Network Linux).  They have requested that optoe be submitted upstream.

The EEPROM data is accessible to user space and kernel consumers via the
nvmem interface.

optoe devices can be configured via device tree or the 'new_device'
paradigm.

See Documentation/misc-devices/optoe.rst for details on configuring
optoe and accessing the EEPROM.

Signed-off-by: Don Bollinger <don@xxxxxxxxxxxxxxxxx>
---
Change in v2:
   - made function optoe_make_regmap() static to fix compiler warnings
Reported-by: kernel test robot <lkp@xxxxxxxxx>
---
 Documentation/devicetree/bindings/eeprom/optoe.txt |  26 +
 Documentation/misc-devices/optoe.rst               | 127 +++
 drivers/misc/eeprom/Kconfig                        |  24 +
 drivers/misc/eeprom/Makefile                       |   1 +
 drivers/misc/eeprom/optoe.c                        | 931 +++++++++++++++++++++
 5 files changed, 1109 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/eeprom/optoe.txt
 create mode 100644 Documentation/misc-devices/optoe.rst
 create mode 100644 drivers/misc/eeprom/optoe.c

diff --git a/Documentation/devicetree/bindings/eeprom/optoe.txt b/Documentation/devicetree/bindings/eeprom/optoe.txt
new file mode 100644
index 000000000000..3a8c350cf2f5
--- /dev/null
+++ b/Documentation/devicetree/bindings/eeprom/optoe.txt
@@ -0,0 +1,26 @@
+EEPROMs on SFP/QSFP/CMIS optoelectronic modules using SFF-8472, SFF-8676,
+CMIS (Common Management Interface Spec) devices.
+
+Required properties:
+- compatible: shall be one of : 
+	'optoe,optoe1' - for QSFP class devices, adhering to SFF-8636
+	'optoe,optoe2' - for SFP class devices, adhering to SFF-8472
+	'optoe,optoe3' - for CMIS devices (newer QSFP class devices)
+- reg: 0x50  The only valid value is 0x50, as all three standards specify that
+  the device is at i2c address 0x50.  (optoe allocates an i2c dummy to access
+  the data at i2c address 0x51.)
+
+Optional property:
+- port_name: can be set to any string up to 19 characters.  Note that the
+  actual mapping between i2c busses and network ports is platform dependent
+  and varies widely.  The 'port_name' property provides a way to associate
+  specific network ports with their associated hardware ports.
+
+Example:
+	#address-cells = <1>;
+	#size-cells = <0>;
+	optoe@50 {
+		compatible = "optoe,optoe2";
+		reg = <0x50>;
+		port_name = "port1";
+	};
diff --git a/Documentation/misc-devices/optoe.rst b/Documentation/misc-devices/optoe.rst
new file mode 100644
index 000000000000..2ffce09f18bb
--- /dev/null
+++ b/Documentation/misc-devices/optoe.rst
@@ -0,0 +1,127 @@
+============================================================
+optoe - EEPROMs on SFP/QSFP/CMIS optoelectronic modules
+============================================================
+
+Author: Don Bollinger (don@xxxxxxxxxxxxxxxxx)
+
+Description:
+============
+
+Optoe is an i2c based driver that supports read/write access to all
+the pages (tables) of MSA standard SFP and similar devices (conforming
+to the SFF-8472 spec), MSA standard QSFP and similar devices (conforming
+to the SFF-8436 or SFF-8636 spec) and CMIS devices (conforming to the
+Common Management Interface Specification).
+
+i2c based optoelectronic transceivers (SPF, QSFP, etc) provide identification,
+operational status, and control registers via an EEPROM model.  Unlike the
+EEPROMs that at24 supports, these devices access data beyond byte 256 via
+a page select register, which must be managed by the driver.  optoe 
+represents the EEPROM as a linear address space, managing the page register
+as needed.  On QSFP and CMIS devices, the first 256 bytes are page 0, followed
+by 128 byte pages 1-128.  On SFP devices, the first 256 bytes are from 
+i2c address 0x50, followed by 256 bytes from i2c address 0x51, followed
+by 128 byte pages 1-128.  See the driver code for a more detailed
+explanation.
+
+The EEPROM data is accessible via an nvmem file, e.g.
+	/sys/bus/nvmem/devices/port1/nvmem
+
+The EEPROM data is also accessible within the kernel via nvmem calls e.g.
+	nvmem = nvmem_device_get(dev, "port1");
+	err = nvmem_device_read(nvmem, offset, length, buffer);
+
+The EEPROM data is also accessible via a bin_attribute file called 'eeprom',
+e.g. 	/sys/bus/i2c/devices/24-0050/eeprom
+
+Device class:
+=============
+
+Note that SFP, QSFP and CMIS type devices are not interchangeable.  The
+driver expects the correct ID (optoe<n>) for each port (each i2c device).
+It does not check because the port will often be empty, and the only way
+to check is to interrogate the device.  Incorrect choice of ID will lead
+to CORRECT data being reported for the first 256 bytes (for any ID, for
+any actual class device).  Data beyond 256 bytes will be INCORRECT if 
+the device doesn't match the optoe<n> type specified.
+
+The device class (1 = QSFP, 2 = SFP, 3 = CMIS) can be read from
+/sys/bus/i2c/devices/<i2c device>/dev_class.  It can also be modified
+by writing to the same file.  This can be useful when upgrading from QSFP
+type devices to CMIS devices (they may have the same form factor) or
+when developing with plug-in adapters to convert  QSFP ports for SFP
+devices.  It is also useful on development hardware that has both types
+of connectors attached to the same i2c bus.
+
+Port name:
+==========
+
+optoe maintains a 'port_name' for each device being managed.  The port name
+is the device name in the nvmem directory, and the dev_name parameter in
+the nvmem_device_get() APIs.
+
+port_name can be set via a device tree property: port_name = "port1";
+
+port_name can also be read/changed by reading/writing to the sysfs file
+/sys/bus/i2c/devices/<i2c device>/port_name.  port_name can be any string,
+up to 19 characters.  If not initialized, port_name will match the i2c
+device name e.g. 1-0050.  If port_name is changed, the nvmem device will
+be changed to match.
+
+Device Tree:
+============
+
+optoe can be instantiated via Device Tree as a child of the i2c bus
+that the device is attached to.
+
+Required properties:
+- compatible: shall be one of : 
+	'optoe,optoe1' - for QSFP class devices, adhering to SFF-8636
+	'optoe,optoe2' - for SFP class devices, adhering to SFF-8472
+	'optoe,optoe3' - for CMIS devices (newer QSFP class devices)
+- reg: 0x50  The only valid value is 0x50, as all three standards specify that
+  the device is at i2c address 0x50.  (optoe allocates an i2c dummy to access
+  the data at i2c address 0x51.)
+
+Optional property:
+- port_name: can be set to any string up to 19 characters.  Note that the
+  actual mapping between i2c busses and network ports is platform dependent
+  and varies widely.  The 'port_name' property provides a way to associate
+  specific network ports with their associated hardware ports.
+
+Example:
+	#address-cells = <1>;
+	#size-cells = <0>;
+	optoe@50 {
+		compatible = "optoe,optoe2";
+		reg = <0x50>;
+		port_name = "port1";
+	};
+
+
+Dynamic installation:
+=====================
+
+Alternatively, optoe can be instantiated with 'new_device', per the convention
+described in Documentation/i2c/instantiating-devices.  It wants one of
+three possible device identifiers, as described above under 'compatible'.
+Use 'optoe1' to indicate this is a QSFP type device, use 'optoe2' to 
+indicate this is an SFP type device, use 'optoe3' to indicate this is a
+CMIS type device.
+
+Example:
+# echo optoe1 0x50 > /sys/bus/i2c/devices/i2c-64/new_device
+# echo port54 > /sys/bus/i2c/devices/i2c-64/port_name
+
+This will add a QSFP type device to i2c bus i2c-64, and name it 'port54'
+
+Example:
+# echo optoe2 0x50 > /sys/bus/i2c/devices/i2c-11/new_device
+# echo port1 > /sys/bus/i2c/devices/i2c-11/port_name
+
+This will add an SFP type device to i2c bus i2c-11, and name it 'port1'
+
+The second parameter to new_device is an i2c address, and MUST be 0x50 for
+this driver to work properly.  This is part of the spec for these devices.
+(It is not necessary to create a device at 0x51 for SFP type devices, the
+driver does that automatically.)
diff --git a/drivers/misc/eeprom/Kconfig b/drivers/misc/eeprom/Kconfig
index 0f791bfdc1f5..17911266d3f6 100644
--- a/drivers/misc/eeprom/Kconfig
+++ b/drivers/misc/eeprom/Kconfig
@@ -129,4 +129,28 @@ config EEPROM_EE1004
 	  This driver can also be built as a module.  If so, the module
 	  will be called ee1004.
 
+config EEPROM_OPTOE
+	tristate "read/write access to SFP*, QSFP* and CMIS EEPROMs"
+	depends on I2C && SYSFS
+	select NVMEM
+	select NVMEM_SYSFS
+	select REGMAP_I2C
+	help
+	  If you say yes here you get support for read and write access to
+	  the EEPROM of SFP, QSFP and CMIS type optical and copper
+	  transceivers.  This includes all devices which conform to SFF-8436
+	  and SFF-8636 (QSFP, QSFP+, QSFP28, etc), SFF-8472 (SFP, SFP+, SFP28,
+	  SFP-DWDM, etc) and Common Management Interface Spec (CMIS, including
+	  QSFP-DD, OSFP, later QSFP*, etc).
+
+	  These devices are usually found in network switches.
+
+	  This driver only manages read/write access to the EEPROM.  Access
+	  to the I/O pins (reset, LPMODE, etc) is still platform specific.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called optoe.
+
+	  If unsure, say N.
+
 endmenu
diff --git a/drivers/misc/eeprom/Makefile b/drivers/misc/eeprom/Makefile
index a9b4b6579b75..e22ef2c05896 100644
--- a/drivers/misc/eeprom/Makefile
+++ b/drivers/misc/eeprom/Makefile
@@ -8,3 +8,4 @@ obj-$(CONFIG_EEPROM_93XX46)	+= eeprom_93xx46.o
 obj-$(CONFIG_EEPROM_DIGSY_MTC_CFG) += digsy_mtc_eeprom.o
 obj-$(CONFIG_EEPROM_IDT_89HPESX) += idt_89hpesx.o
 obj-$(CONFIG_EEPROM_EE1004)	+= ee1004.o
+obj-$(CONFIG_EEPROM_OPTOE)	+= optoe.o
diff --git a/drivers/misc/eeprom/optoe.c b/drivers/misc/eeprom/optoe.c
new file mode 100644
index 000000000000..5f6db43ca6be
--- /dev/null
+++ b/drivers/misc/eeprom/optoe.c
@@ -0,0 +1,931 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * optoe.c - A driver to read and write the EEPROM on optical transceivers
+ * (SFP, QSFP, CMIS (Common Management Interface Spec)
+ * and similar I2C based devices)
+ *
+ * Copyright (C) 2014 Cumulus networks Inc.
+ * Copyright (C) 2017 Finisar Corp.
+ */
+
+/*
+ *	Description:
+ *	a) Optical transceiver EEPROM read/write transactions are just like
+ *		the at24 eeproms managed by the at24.c i2c driver
+ *	b) The register/memory layout is up to 256 128 byte pages defined by
+ *		a "pages valid" register and switched via a "page select"
+ *		register as explained in below diagram.
+ *	c) 256 bytes are mapped at a time. 'Lower page 00h' is the first 128
+ *	        bytes of address space, and always references the same
+ *	        location, independent of the page select register.
+ *	        All mapped pages are mapped into the upper 128 bytes
+ *	        (offset 128-255) of the i2c address.
+ *	d) Devices with one I2C address (eg QSFP, CMIS) use I2C address 0x50
+ *		(A0h in the spec), and map all pages in the upper 128 bytes
+ *		of that address.
+ *	e) Devices with two I2C addresses (eg SFP) have 256 bytes of data
+ *		at I2C address 0x50, and 256 bytes of data at I2C address
+ *		0x51 (A2h in the spec).  Page selection and paged access
+ *		only apply to this second I2C address (0x51).
+ *	e) The address space is presented, by the driver, as a linear
+ *	        address space.  For devices with one I2C client at address
+ *	        0x50 (eg QSFP, CMIS), offset 0-127 are in the lower
+ *	        half of address 50/A0h/optoe_client.  Offset 128-255 are in
+ *	        page 0, 256-383 are page 1, etc.  More generally, offset
+ *	        'n' resides in page (n/128)-1.  ('page -1' is the lower
+ *	        half, offset 0-127).
+ *	f) For devices with two I2C clients at address 0x50 and 0x51 (eg SFP),
+ *		the address space places offset 0-127 in the lower
+ *	        half of 50/A0/optoe_client, offset 128-255 in the upper
+ *	        half.  Offset 256-383 is in the lower half of 51/A2/dummy.
+ *	        Offset 384-511 is in page 0, in the upper half of 51/A2/...
+ *	        Offset 512-639 is in page 1, in the upper half of 51/A2/...
+ *	        Offset 'n' is in page (n/128)-3 (for n > 383)
+ *
+ *	                    One I2c addressed (eg QSFP, CMIS) Memory Map
+ *
+ *	                    2-Wire Serial Address: 1010000x
+ *
+ *	                    Lower Page 00h (128 bytes)
+ *	                    =====================
+ *	                   |                     |
+ *	                   |                     |
+ *	                   |                     |
+ *	                   |                     |
+ *	                   |                     |
+ *	                   |                     |
+ *	                   |                     |
+ *	                   |                     |
+ *	                   |                     |
+ *	                   |                     |
+ *	                   |Page Select Byte(127)|
+ *	                    =====================
+ *	                              |
+ *	                              |
+ *	                              V
+ *	     ------------------------------------------------------------
+ *	    |                 |                  |                       |
+ *	    |                 |                  |                       |
+ *	    V                 V                  V                       V
+ *	 ------------   --------------      ---------------     --------------
+ *	|            | |              |    |               |   |              |
+ *	|   Upper    | |     Upper    |    |     Upper     |   |    Upper     |
+ *	|  Page 00h  | |    Page 01h  |    |    Page 02h   |   |   Page 03h   |
+ *	|            | |   (Optional) |    |   (Optional)  |   |  (Optional   |
+ *	|            | |              |    |               |   |   for Cable  |
+ *	|            | |              |    |               |   |  Assemblies) |
+ *	|    ID      | |     AST      |    |      User     |   |              |
+ *	|  Fields    | |    Table     |    |   EEPROM Data |   |              |
+ *	|            | |              |    |               |   |              |
+ *	|            | |              |    |               |   |              |
+ *	|            | |              |    |               |   |              |
+ *	 ------------   --------------      ---------------     --------------
+ *
+ * The SFF 8636 (QSFP) spec only defines the 4 pages described above.
+ * In anticipation of future applications and devices, this driver
+ * supports access to the full architected range, 256 pages.
+ *
+ * The CMIS (Common Management Interface Specification) defines use of
+ * considerably more pages (at least to page 0xAF), which this driver
+ * supports.
+ *
+ * NOTE: This version of the driver ONLY SUPPORTS BANK 0 PAGES on CMIS
+ * devices.
+ *
+ **/
+
+/* #define DEBUG 1 */
+
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/nvmem-provider.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+
+/* The maximum length of a port name */
+#define MAX_PORT_NAME_LEN 20
+
+/* fundamental unit of addressing for EEPROM */
+#define OPTOE_PAGE_SIZE 128
+/*
+ * Single address devices (eg QSFP, CMIS) have 256 pages, plus the unpaged
+ * low 128 bytes.  If the device does not support paging, it is
+ * only 2 'pages' long.
+ */
+#define OPTOE_ARCH_PAGES 256
+#define ONE_ADDR_EEPROM_SIZE ((1 + OPTOE_ARCH_PAGES) * OPTOE_PAGE_SIZE)
+#define ONE_ADDR_EEPROM_UNPAGED_SIZE (2 * OPTOE_PAGE_SIZE)
+/*
+ * Dual address devices (eg SFP) have 256 pages, plus the unpaged
+ * low 128 bytes, plus 256 bytes at 0x50.  If the device does not
+ * support paging, it is 4 'pages' long.
+ */
+#define TWO_ADDR_EEPROM_SIZE ((3 + OPTOE_ARCH_PAGES) * OPTOE_PAGE_SIZE)
+#define TWO_ADDR_EEPROM_UNPAGED_SIZE (4 * OPTOE_PAGE_SIZE)
+#define TWO_ADDR_NO_0X51_SIZE (2 * OPTOE_PAGE_SIZE)
+
+/* a few constants to find our way around the EEPROM */
+#define OPTOE_PAGE_SELECT_REG   0x7F
+#define ONE_ADDR_PAGEABLE_REG 0x02
+#define QSFP_NOT_PAGEABLE (1<<2)
+#define CMIS_NOT_PAGEABLE (1<<7)
+#define TWO_ADDR_PAGEABLE_REG 0x40
+#define TWO_ADDR_PAGEABLE (1<<4)
+#define TWO_ADDR_0X51_REG 92
+#define TWO_ADDR_0X51_SUPP (1<<6)
+#define OPTOE_READ_OP 0
+#define OPTOE_WRITE_OP 1
+#define OPTOE_EOF 0  /* used for access beyond end of device */
+
+/* define optoe_client structure to tie the i2c client to its regmap */
+struct optoe_client {
+	struct i2c_client *client;
+	struct regmap *regmap;
+};
+
+struct optoe_data {
+	char port_name[MAX_PORT_NAME_LEN];
+	u32 byte_len;		/* architected size of EEPROM */
+
+	/*
+	 * Lock protects against activities from other Linux tasks,
+	 * but not from changes by other I2C masters.
+	 */
+	struct mutex lock;
+	struct attribute_group attr_group;
+	struct nvmem_device *nvmem;
+
+	unsigned int write_max;
+
+	/* dev_class: ONE_ADDR (QSFP), TWO_ADDR (SFP), or CMIS */
+	int dev_class;
+
+	/* client at 0x50 */
+	struct optoe_client optoe_client;
+	/* dummy at 0x51 for SFP devices */
+	struct optoe_client optoe_dummy;
+};
+
+/*
+ * specs often allow 5 msec for a page write, sometimes 20 msec;
+ * it's important to recover from write timeouts.
+ */
+static unsigned int write_timeout = 25;
+
+/*
+ * flags to distinguish one-address (QSFP family) from two-address (SFP family)
+ * and one-address Common Management Interface Specification (CMIS family)
+ */
+#define ONE_ADDR 1
+#define TWO_ADDR 2
+#define CMIS_ADDR 3
+
+static const struct i2c_device_id optoe_ids[] = {
+	{ "optoe1", ONE_ADDR },
+	{ "optoe2", TWO_ADDR },
+	{ "optoe3", CMIS_ADDR },
+	{ /* END OF LIST */ }
+};
+MODULE_DEVICE_TABLE(i2c, optoe_ids);
+
+/*-------------------------------------------------------------------------*/
+/*
+ * optoe_translate_offset() computes the addressing information to be used for
+ * a given r/w request.
+ *
+ * Task is to calculate the client (optoe_client for addr 50,
+ * optoe_dummy for addr 51) the page, and the offset.
+ *
+ * Handles both single address (QSFP), two address (SFP) and CMIS devices.
+ *     For SFP, offset 0-255 are on optoe_client, >255 is on optoe_dummy
+ *     Offset 256-383 are on the lower half of optoe_dummy
+ *     Pages are accessible on the upper half of optoe_dummy
+ *     Offset >383 are in 128 byte pages mapped into the upper half
+ *
+ *     For QSFP and CMIS, all offsets are on optoe_client
+ *     offset 0-127 are on the lower half of optoe_client (no paging)
+ *     Pages are accessible on the upper half of optoe_client.
+ *     Offset >127 are in 128 byte pages mapped into the upper half
+ *
+ *     Callers must not read/write beyond the end of a client or a page
+ *     without recomputing the client/page.  Hence offset (within page)
+ *     plus length must be less than or equal to 128.  (Note that this
+ *     routine does not have access to the length of the call, hence
+ *     cannot do the validity check.)
+ *
+ * Offset within Lower Page 00h and Upper Page 00h are not recomputed
+ */
+
+static uint8_t optoe_translate_offset(struct optoe_data *optoe,
+		loff_t *offset, struct optoe_client **optoe_client)
+{
+	unsigned int page = 0;
+
+	*optoe_client = &optoe->optoe_client;
+
+	/* if SFP style, offset > 255, shift to i2c addr 0x51 */
+	if (optoe->dev_class == TWO_ADDR) {
+		if (*offset > 255) {
+			/* like QSFP, but shifted dummy client */
+			*optoe_client = &optoe->optoe_dummy;
+			*offset -= 256;
+		}
+	}
+
+	/*
+	 * if offset is in the range 0-128...
+	 * page doesn't matter (using lower half), return 0.
+	 * offset is already correct (don't add 128 to get to paged area)
+	 */
+	if (*offset < OPTOE_PAGE_SIZE)
+		return page;
+
+	/* note, page will always be positive since *offset >= 128 */
+	page = (*offset >> 7)-1;
+	/*
+	 * OPTOE_PAGE_SIZE puts offset in the top half (the paged area),
+	 * offset within the top half is last 7 bits
+	 */
+	*offset = OPTOE_PAGE_SIZE + (*offset & 0x7f);
+
+	return page;  /* note also returning client and offset */
+}
+
+static int optoe_regmap_rw(struct optoe_data *optoe,
+				struct optoe_client *optoe_client,
+				char *buf,
+				unsigned int offset,
+				size_t count, int opcode)
+{
+	unsigned long timeout, access_time;
+	struct i2c_client *client = optoe_client->client;
+	struct regmap *regmap = optoe_client->regmap;
+	int ret;
+
+	/*
+	 * Accesses fail if the previous write didn't complete yet. We may
+	 * loop a few times until this one succeeds, waiting at least
+	 * long enough for one entire page write to work.
+	 */
+	timeout = jiffies + msecs_to_jiffies(write_timeout);
+	do {
+		access_time = jiffies;
+
+		if (opcode == OPTOE_READ_OP) {
+			ret = regmap_bulk_read(regmap, offset, buf, count);
+		} else {
+			/* write_max is always 1 in this driver */
+			if (count > optoe->write_max)
+				count = optoe->write_max;
+			ret = regmap_bulk_write(regmap, offset, buf, count);
+		}
+		dev_dbg(&client->dev, "regmap %s %zu@%d --> %d (%lu)\n",
+			(opcode == OPTOE_READ_OP) ? "read" : "write",
+			count, offset, ret, jiffies);
+		if (!ret)   /* regmap_bulk_calls returns 0 on success */
+			return count;
+
+		usleep_range(1000, 2000);
+	} while (time_before(access_time, timeout));
+
+	return -ETIMEDOUT;
+}
+
+static int optoe_eeprom_update_client(struct optoe_data *optoe,
+				char *buf, loff_t off,
+				size_t count, int opcode)
+{
+	struct optoe_client *optoe_client;
+	uint8_t page = 0;
+	loff_t phy_offset = off;
+	int retval = 0;
+	int ret = 0;
+	int status;
+	struct device *dev = &optoe->optoe_client.client->dev;
+
+	/* translate offset into page, 'offset within page' */
+	page = optoe_translate_offset(optoe, &phy_offset, &optoe_client);
+	dev_dbg(dev,
+		"%s off %lld  page:%d phy_offset:%lld, count:%ld, opcode:%d\n",
+		__func__, off, page, phy_offset, (long) count, opcode);
+	/* set the page register */
+	if (page > 0) {
+		ret = optoe_regmap_rw(optoe, optoe_client, &page,
+			OPTOE_PAGE_SELECT_REG, 1, OPTOE_WRITE_OP);
+		if (ret < 0) {
+			dev_dbg(dev,
+				"Page register write, page %d failed:%d!\n",
+				page, ret);
+			return ret;
+		}
+	}
+
+	/* read/write the data */
+	while (count) {
+
+		status =  optoe_regmap_rw(optoe, optoe_client,
+			buf, phy_offset, count, opcode);
+
+		if (status <= 0) {
+			if (retval == 0)
+				retval = status;
+			break;
+		}
+		buf += status;
+		phy_offset += status;
+		count -= status;
+		retval += status;
+	}
+
+
+	/*
+	 * return the page register to page 0 - why?
+	 * We either have to set the page register to 0 on every access
+	 * to it, or restore it to 0 whenever we change it.  Otherwise,
+	 * accesses to page 0 would actually go to whatever the last page
+	 * was.  Assume more accesses to page 0 than all other pages
+	 * combined, so less total accesses if we always leave it at page 0
+	 */
+	if (page > 0) {
+		page = 0;
+		ret = optoe_regmap_rw(optoe, optoe_client, &page,
+			OPTOE_PAGE_SELECT_REG, 1, OPTOE_WRITE_OP);
+		if (ret < 0) {
+			dev_err(dev,
+				"Restore page register to 0 failed:%d!\n", ret);
+			/* error only if nothing has been transferred */
+			if (retval == 0)
+				retval = ret;
+		}
+	}
+	return retval;
+}
+
+/*
+ * Figure out if this access is within the range of supported pages.
+ * Note this is called on every access because we don't know if the
+ * module has been replaced since the last call.
+ *
+ * Returns updated len for this access:
+ *     - entire access is legal, original len is returned.
+ *     - access begins legal but is too long, len is truncated to fit.
+ *     - initial offset exceeds supported pages, return OPTOE_EOF (zero)
+ */
+static int optoe_page_legal(struct optoe_data *optoe,
+		loff_t off, size_t len)
+{
+	struct optoe_client *optoe_client = &optoe->optoe_client;
+	u8 regval;
+	int not_pageable;
+	int status;
+	size_t maxlen;
+	struct device *dev = &optoe_client->client->dev;
+
+	if (off < 0)
+		return -EINVAL;
+	if (optoe->dev_class == TWO_ADDR) {
+		/* SFP case */
+		/* if only using addr 0x50 (first 256 bytes) we're good */
+		if ((off + len) <= TWO_ADDR_NO_0X51_SIZE)
+			return len;
+		/* if offset exceeds possible pages, we're not good */
+		if (off >= TWO_ADDR_EEPROM_SIZE)
+			return OPTOE_EOF;
+		/* in between, are pages supported? */
+		status = optoe_regmap_rw(optoe, optoe_client, &regval,
+				TWO_ADDR_PAGEABLE_REG, 1, OPTOE_READ_OP);
+		if (status < 0)
+			return status;  /* error out (no module?) */
+		if (regval & TWO_ADDR_PAGEABLE) {
+			/* Pages supported, trim len to the end of pages */
+			maxlen = TWO_ADDR_EEPROM_SIZE - off;
+		} else {
+			/* pages not supported, trim len to unpaged size */
+			if (off >= TWO_ADDR_EEPROM_UNPAGED_SIZE)
+				return OPTOE_EOF;
+
+			/* will be accessing addr 0x51, is that supported? */
+			/* byte 92, bit 6 implies DDM support, 0x51 support */
+			status = optoe_regmap_rw(optoe, optoe_client, &regval,
+						TWO_ADDR_0X51_REG, 1,
+						OPTOE_READ_OP);
+			if (status < 0)
+				return status;
+			if (regval & TWO_ADDR_0X51_SUPP) {
+				/* addr 0x51 is OK */
+				maxlen = TWO_ADDR_EEPROM_UNPAGED_SIZE - off;
+			} else {
+				/* addr 0x51 NOT supported, trim to 256 max */
+				if (off >= TWO_ADDR_NO_0X51_SIZE)
+					return OPTOE_EOF;
+				maxlen = TWO_ADDR_NO_0X51_SIZE - off;
+			}
+		}
+		len = (len > maxlen) ? maxlen : len;
+	} else {
+		/* QSFP case, CMIS case */
+		/* if no pages needed, we're good */
+		if ((off + len) <= ONE_ADDR_EEPROM_UNPAGED_SIZE)
+			return len;
+		/* if offset exceeds possible pages, we're not good */
+		if (off >= ONE_ADDR_EEPROM_SIZE)
+			return OPTOE_EOF;
+		/* in between, are pages supported? */
+		status = optoe_regmap_rw(optoe, optoe_client, &regval,
+				ONE_ADDR_PAGEABLE_REG, 1, OPTOE_READ_OP);
+		if (status < 0)
+			return status;  /* error out (no module?) */
+
+		/*
+		 * note CMIS put the pageable bit in the same register
+		 * as QSFP, but at a different bit :-(
+		 */
+		if (optoe->dev_class == ONE_ADDR)
+			not_pageable = QSFP_NOT_PAGEABLE;
+		else
+			not_pageable = CMIS_NOT_PAGEABLE;
+		if (regval & not_pageable) {
+			/* pages not supported, trim len to unpaged size */
+			if (off >= ONE_ADDR_EEPROM_UNPAGED_SIZE)
+				return OPTOE_EOF;
+			maxlen = ONE_ADDR_EEPROM_UNPAGED_SIZE - off;
+		} else {
+			/* Pages supported, trim len to the end of pages */
+			maxlen = ONE_ADDR_EEPROM_SIZE - off;
+		}
+		len = (len > maxlen) ? maxlen : len;
+	}
+	dev_dbg(dev, "page_legal, class %d, off %lld len %ld\n",
+		optoe->dev_class, off, (long) len);
+	return len;
+}
+
+static int optoe_read_write(struct optoe_data *optoe,
+		char *buf, loff_t off, size_t len, int opcode)
+{
+	struct i2c_client *client = optoe->optoe_client.client;
+	int chunk;
+	int status = 0;
+	int retval;
+	size_t pending_len = 0, chunk_len = 0;
+	loff_t chunk_offset = 0, chunk_start_offset = 0;
+	loff_t chunk_end_offset = 0;
+
+	dev_dbg(&client->dev, "%s: off %lld  len:%ld, opcode:%s\n",
+		__func__, off, (long) len,
+		(opcode == OPTOE_READ_OP) ? "r" : "w");
+	if (unlikely(!len))
+		return len;
+
+	/*
+	 * Read data from chip, protecting against concurrent updates
+	 * from this host, but not from other I2C masters.
+	 */
+	mutex_lock(&optoe->lock);
+
+	/*
+	 * Confirm this access fits within the device suppored addr range
+	 */
+	status = optoe_page_legal(optoe, off, len);
+
+	/*
+	 * returning 0 (OPTOE_EOF) on a write call gets into an infinite
+	 * loop with the regmap/i2c code.  Returning an error on a read call
+	 * will show up as an error with 'cat <eeprom file>'.  So, writing
+	 * past EOF is an error, reading past EOF is just '0'
+	 */
+	if ((status == OPTOE_EOF) && (opcode == OPTOE_WRITE_OP))
+		status = -EINVAL;
+
+	if ((status == OPTOE_EOF) || (status < 0)) {
+		mutex_unlock(&optoe->lock);
+		return status;
+	}
+	len = status;
+
+	/*
+	 * For each (128 byte) chunk involved in this request, issue a
+	 * separate call to optoe_eeprom_update_client(), to
+	 * ensure that each access recalculates the client/page
+	 * and writes the page register as needed.
+	 * Note that chunk to page mapping is confusing, is different for
+	 * QSFP/CMIS and SFP, and never needs to be done.  Don't try!
+	 */
+	pending_len = len; /* amount remaining to transfer */
+	retval = 0;  /* amount transferred */
+	for (chunk = off >> 7; chunk <= (off + len - 1) >> 7; chunk++) {
+
+		/*
+		 * Compute the offset and number of bytes to be read/written
+		 *
+		 * 1. start at an offset not equal to 0 (within the chunk)
+		 *    and read/write less than the rest of the chunk
+		 * 2. start at an offset not equal to 0 and read/write the rest
+		 *    of the chunk
+		 * 3. start at offset 0 (within the chunk) and read/write less
+		 *    than entire chunk
+		 * 4. start at offset 0 (within the chunk), and read/write
+		 *    the entire chunk
+		 */
+		chunk_start_offset = chunk * OPTOE_PAGE_SIZE;
+		chunk_end_offset = chunk_start_offset + OPTOE_PAGE_SIZE;
+
+		if (chunk_start_offset < off) {
+			chunk_offset = off;
+			if ((off + pending_len) < chunk_end_offset)
+				chunk_len = pending_len;
+			else
+				chunk_len = chunk_end_offset - off;
+		} else {
+			chunk_offset = chunk_start_offset;
+			if (pending_len < OPTOE_PAGE_SIZE)
+				chunk_len = pending_len;
+			else
+				chunk_len = OPTOE_PAGE_SIZE;
+		}
+
+		/*
+		 * note: chunk_offset is from the start of the EEPROM,
+		 * not the start of the chunk
+		 */
+		status = optoe_eeprom_update_client(optoe, buf,
+				chunk_offset, chunk_len, opcode);
+		if (status != chunk_len) {
+			/* This is another 'no device present' path */
+			dev_dbg(&client->dev,
+			"o_u_c: chunk %d c_offset %lld c_len %ld failed %d!\n",
+			chunk, chunk_offset, (long) chunk_len, status);
+			if (status > 0)
+				retval += status;
+			if (retval == 0)
+				retval = status;
+			break;
+		}
+		buf += status;
+		pending_len -= status;
+		retval += status;
+	}
+	mutex_unlock(&optoe->lock);
+
+	return retval;
+}
+
+static int optoe_nvmem_read(void *priv, unsigned int off,
+			    void *buf, size_t count)
+{
+	struct optoe_data *optoe = priv;
+
+	return optoe_read_write(optoe, buf, off, count, OPTOE_READ_OP);
+}
+
+static int optoe_nvmem_write(void *priv, unsigned int off,
+			    void *buf, size_t count)
+{
+	struct optoe_data *optoe = priv;
+
+	return optoe_read_write(optoe, buf, off, count, OPTOE_WRITE_OP);
+}
+
+static int optoe_remove(struct i2c_client *client)
+{
+	struct optoe_data *optoe;
+
+	optoe = i2c_get_clientdata(client);
+	sysfs_remove_group(&client->dev.kobj, &optoe->attr_group);
+	kfree(optoe);
+	return 0;
+}
+
+
+/*
+ * optoe_make_regmap creates the regmap for the client.
+ * IMPORTANT: Don't call the regmap read/write calls directly
+ * for these devices.  These devices are paged, and you have to
+ * set the page register before accessing the data in that page.
+ * Use the nvmem interfaces, those read/write calls use this
+ * driver to manage pages correctly.
+ */
+static struct regmap *optoe_make_regmap(struct i2c_client *client)
+{
+	struct regmap_config regmap_config = { };
+	struct regmap *regmap;
+
+	/* setup a minimal regmap - 8 bits, 8 bit addresses */
+	regmap_config.val_bits = 8;
+	regmap_config.reg_bits = 8;
+
+	/* I'll handle the locking */
+	regmap_config.disable_locking = true;
+	regmap = devm_regmap_init_i2c(client, &regmap_config);
+	return regmap;
+}
+
+/*
+ * optoe_make_nvmem() unregisters the existing optoe->nvmem if it
+ * exists, then registers a new one.  Convenient when the size
+ * of an EEPROM device changes.
+ */
+static int optoe_make_nvmem(struct optoe_data *optoe)
+{
+	struct nvmem_config nvmem_config = { };
+	struct i2c_client *client = optoe->optoe_client.client;
+	struct device *dev = &client->dev;
+
+	nvmem_config.name = optoe->port_name;
+	/* NVMEM_DEVID_NONE tells nvmem not to append '0' to name */
+	nvmem_config.id = NVMEM_DEVID_NONE;
+	nvmem_config.dev = dev;
+	nvmem_config.read_only = false;
+	nvmem_config.root_only = false;
+	nvmem_config.owner = THIS_MODULE;
+	nvmem_config.compat = true;
+	nvmem_config.base_dev = dev;
+	nvmem_config.reg_read = optoe_nvmem_read;
+	nvmem_config.reg_write = optoe_nvmem_write;
+	nvmem_config.priv = optoe;
+	nvmem_config.stride = 1;
+	nvmem_config.word_size = 1;
+	nvmem_config.size = optoe->byte_len;
+	if (optoe->nvmem)
+		devm_nvmem_unregister(dev, optoe->nvmem);
+	optoe->nvmem = devm_nvmem_register(dev, &nvmem_config);
+	dev_info(dev, "%u byte class %d EEPROM\n",
+		optoe->byte_len, optoe->dev_class);
+	return 0;
+}
+
+static ssize_t dev_class_show(struct device *dev,
+			struct device_attribute *dattr, char *buf)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct optoe_data *optoe = i2c_get_clientdata(client);
+	ssize_t count;
+
+	mutex_lock(&optoe->lock);
+	count = sprintf(buf, "%d\n", optoe->dev_class);
+	mutex_unlock(&optoe->lock);
+
+	return count;
+}
+
+static ssize_t dev_class_store(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct optoe_data *optoe = i2c_get_clientdata(client);
+	int dev_class;
+	struct regmap *regmap;
+	ssize_t err;
+
+	/*
+	 * dev_class is actually the number of i2c addresses used, thus
+	 * legal values are "1" (QSFP class) and "2" (SFP class)
+	 * And...  CMIS spec is 1 i2c address, but puts the pageable
+	 * bit in a different location, so CMIS devices are "3"
+	 */
+
+	if (kstrtoint(buf, 0, &dev_class) != 0 ||
+		dev_class < 1 || dev_class > 3)
+		return -EINVAL;
+
+	if (optoe->dev_class == dev_class)  /* no change, NOP */
+		return(count);
+
+	mutex_lock(&optoe->lock);
+	if (dev_class == TWO_ADDR) {
+		/* SFP family */
+		/* if it doesn't exist, create 0x51 i2c address */
+		if (!optoe->optoe_dummy.client) {
+			optoe->optoe_dummy.client =
+				devm_i2c_new_dummy_device(dev,
+							  client->adapter,
+							  0x51);
+			if (!optoe->optoe_dummy.client) {
+				dev_err(&client->dev,
+					"address 0x51 unavailable\n");
+				mutex_unlock(&optoe->lock);
+				return -EADDRINUSE;
+			}
+			regmap = optoe_make_regmap(
+					optoe->optoe_dummy.client);
+			if (IS_ERR(regmap)) {
+				mutex_unlock(&optoe->lock);
+				return PTR_ERR(regmap);
+			}
+			optoe->optoe_dummy.regmap = regmap;
+		}
+		optoe->byte_len = TWO_ADDR_EEPROM_SIZE;
+	} else {
+		/* one-address (eg QSFP) and CMIS family */
+		/* note, no need to delete the dummy i2c device */
+		optoe->byte_len = ONE_ADDR_EEPROM_SIZE;
+	}
+	optoe->dev_class = dev_class;
+	optoe_make_nvmem(optoe);  /* updates the reported size of EEPROM */
+	err = (IS_ERR(optoe->nvmem)) ? PTR_ERR(optoe->nvmem) : 0;
+	mutex_unlock(&optoe->lock);
+
+	return err;
+}
+
+static ssize_t port_name_show(struct device *dev,
+			struct device_attribute *dattr, char *buf)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct optoe_data *optoe = i2c_get_clientdata(client);
+	ssize_t count;
+
+	mutex_lock(&optoe->lock);
+	count = sprintf(buf, "%s\n", optoe->port_name);
+	mutex_unlock(&optoe->lock);
+
+	return count;
+}
+
+static ssize_t port_name_store(struct device *dev,
+			struct device_attribute *attr,
+			const char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct optoe_data *optoe = i2c_get_clientdata(client);
+	char port_name[MAX_PORT_NAME_LEN];
+
+	/* no checking, this value is not used except by port_name_show */
+
+	if (sscanf(buf, "%19s", port_name) != 1)
+		return -EINVAL;
+
+	mutex_lock(&optoe->lock);
+	strcpy(optoe->port_name, port_name);
+	optoe_make_nvmem(optoe);  /* updates the name of the nvmem */
+	mutex_unlock(&optoe->lock);
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(port_name);
+
+static DEVICE_ATTR_RW(dev_class);
+
+
+static struct attribute *optoe_attrs[] = {
+	&dev_attr_port_name.attr,
+	&dev_attr_dev_class.attr,
+	NULL,
+};
+
+static struct attribute_group optoe_attr_group = {
+	.attrs = optoe_attrs,
+};
+
+static int optoe_probe(struct i2c_client *client)
+{
+	struct regmap *regmap;
+	int err;
+	struct optoe_data *optoe;
+	const char *of_port_name = NULL;
+	struct device *dev = &client->dev;
+
+	if (client->addr != 0x50) {
+		dev_dbg(dev, "probe, bad i2c addr: 0x%x\n", client->addr);
+		err = -EINVAL;
+		goto exit;
+	}
+
+	optoe = kzalloc(sizeof(struct optoe_data), GFP_KERNEL);
+	if (!optoe) {
+		err = -ENOMEM;
+		goto exit;
+	}
+	mutex_init(&optoe->lock);
+
+	/*
+	 * if the port_name property is defined, use it, else use the
+	 * device name as port_name
+	 */
+	if (device_property_present(dev, "port_name")) {
+		err = device_property_read_string(dev, "port_name",
+						  &of_port_name);
+		if (err)
+			of_port_name = dev_name(dev);
+	} else {
+		of_port_name = dev_name(dev);
+	}
+	memcpy(optoe->port_name, of_port_name, MAX_PORT_NAME_LEN);
+
+	/* determine whether this is a one-address or two-address module */
+	if (strcmp(client->name, "optoe1") == 0) {
+		/* QSFP family */
+		optoe->dev_class = ONE_ADDR;
+		optoe->byte_len = ONE_ADDR_EEPROM_SIZE;
+	} else if (strcmp(client->name, "optoe2") == 0) {
+		/* SFP family */
+		optoe->dev_class = TWO_ADDR;
+		optoe->byte_len = TWO_ADDR_EEPROM_SIZE;
+	} else if (strcmp(client->name, "optoe3") == 0) {
+		/* CMIS spec */
+		optoe->dev_class = CMIS_ADDR;
+		optoe->byte_len = ONE_ADDR_EEPROM_SIZE;
+	} else {     /* those were the only choices */
+		err = -EINVAL;
+		goto exit;
+	}
+
+	/*
+	 * Old application notes recommend 1 byte writes for some
+	 * modules.  This could probably be lifted, but lacking
+	 * a broad base of devices and systems to test, I'm leaving
+	 * this as is.  If this is ever raised, the max would automatically
+	 * be 128 bytes as anything larger would cross page
+	 * boundaries with wraparound effects.
+	 * TODO: Consider making this a device tree property
+	 */
+
+	optoe->write_max = 1;
+
+	regmap = optoe_make_regmap(client);
+	if (IS_ERR(regmap)) {
+		err = PTR_ERR(regmap);
+		goto exit;
+	}
+
+	optoe->optoe_client.client = client;
+	optoe->optoe_client.regmap = regmap;
+
+	/* SFF-8472 spec requires that the second I2C address be 0x51 */
+	if (optoe->dev_class == TWO_ADDR) {
+		optoe->optoe_dummy.client =
+			devm_i2c_new_dummy_device(dev, client->adapter, 0x51);
+		if (!optoe->optoe_dummy.client) {
+			dev_err(dev, "address 0x51 unavailable\n");
+			err = -EADDRINUSE;
+			goto err_struct;
+		}
+		regmap = optoe_make_regmap(optoe->optoe_dummy.client);
+		if (IS_ERR(regmap)) {
+			err = PTR_ERR(regmap);
+			goto err_struct;
+		}
+		optoe->optoe_dummy.regmap = regmap;
+	}
+
+	optoe->attr_group = optoe_attr_group;
+
+	err = sysfs_create_group(&client->dev.kobj, &optoe->attr_group);
+	if (err) {
+		dev_err(dev, "failed to create sysfs attribute group.\n");
+		goto err_struct;
+	}
+
+	i2c_set_clientdata(client, optoe);
+	optoe_make_nvmem(optoe);
+	if (IS_ERR(optoe->nvmem)) {
+		err = PTR_ERR(optoe->nvmem);
+		goto err_struct;
+	}
+
+	return 0;
+
+err_struct:
+	kfree(optoe);
+exit:
+	dev_dbg(dev, "probe error %d\n", err);
+
+	return err;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static struct i2c_driver optoe_driver = {
+	.driver = {
+		.name = "optoe",
+		.owner = THIS_MODULE,
+	},
+	.probe_new = optoe_probe,
+	.remove = optoe_remove,
+	.id_table = optoe_ids,
+};
+
+static int __init optoe_init(void)
+{
+	return i2c_add_driver(&optoe_driver);
+}
+module_init(optoe_init);
+
+static void __exit optoe_exit(void)
+{
+	i2c_del_driver(&optoe_driver);
+}
+module_exit(optoe_exit);
+
+MODULE_DESCRIPTION("Driver for optical transceiver (SFP/QSFP/CMIS) EEPROMs");
+MODULE_AUTHOR("DON BOLLINGER <don@xxxxxxxxxxxxxxxxx>");
+MODULE_LICENSE("GPL");

base-commit: a2ea4e1d9091cd8bc69f1c42c15bedc38618f04c
-- 
2.11.0