Re: [PATCH v2 2/3] platform/chrome: Support reading/writing the vboot context
From: Emilio LÃpez
Date: Tue Sep 15 2015 - 15:16:32 EST
Hi Javier,
Thanks for the review. You'll find my answers inline
On 15/09/15 10:47, Javier Martinez Canillas wrote:
Hello Emilio,
Patch looks mostly good to me, I just have a few comments.
On Mon, Sep 14, 2015 at 2:34 PM, Emilio LÃpez
<emilio.lopez@xxxxxxxxxxxxxxx> wrote:
Some EC implementations include a small nvram space used to store
verified boot context data. This patch offers a way to expose this
data to userspace.
Signed-off-by: Emilio LÃpez <emilio.lopez@xxxxxxxxxxxxxxx>
---
Changes from v1:
- Use is_bin_visible instead of is_visible
Documentation/devicetree/bindings/mfd/cros-ec.txt | 4 +
drivers/platform/chrome/Makefile | 5 +-
drivers/platform/chrome/cros_ec_dev.c | 1 +
drivers/platform/chrome/cros_ec_vbc.c | 137 ++++++++++++++++++++++
include/linux/mfd/cros_ec.h | 1 +
5 files changed, 147 insertions(+), 1 deletion(-)
create mode 100644 drivers/platform/chrome/cros_ec_vbc.c
diff --git a/Documentation/devicetree/bindings/mfd/cros-ec.txt b/Documentation/devicetree/bindings/mfd/cros-ec.txt
index 1777916..136e0c2 100644
--- a/Documentation/devicetree/bindings/mfd/cros-ec.txt
+++ b/Documentation/devicetree/bindings/mfd/cros-ec.txt
@@ -34,6 +34,10 @@ Required properties (LPC):
- compatible: "google,cros-ec-lpc"
- reg: List of (IO address, size) pairs defining the interface uses
+Optional properties (all):
+- google,has-vbc-nvram: Some implementations of the EC include a small
+ nvram space used to store verified boot context data. This boolean flag
+ is used to specify whether this nvram is present or not.
Example for I2C:
I would split the DT binding part from the actual implementation, see
Documentation/devicetree/bindings/submitting-patches.txt.
Ok, I'll do
diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
index 4a11b01..787be61 100644
--- a/drivers/platform/chrome/Makefile
+++ b/drivers/platform/chrome/Makefile
@@ -1,7 +1,10 @@
obj-$(CONFIG_CHROMEOS_LAPTOP) += chromeos_laptop.o
obj-$(CONFIG_CHROMEOS_PSTORE) += chromeos_pstore.o
-cros_ec_devs-objs := cros_ec_dev.o cros_ec_sysfs.o cros_ec_lightbar.o
+cros_ec_devs-objs := cros_ec_dev.o
+cros_ec_devs-objs += cros_ec_lightbar.o
+cros_ec_devs-objs += cros_ec_sysfs.o
+cros_ec_devs-objs += cros_ec_vbc.o
Why are you changing the Makefile? AFAIK += is usually used when the
compilation is conditional based on a Kconfig symbol but since these
are build unconditionally, I'll just keep it as foo := bar baz
As far as I'm aware, += is append[0]. It's used for stuff like
obj-$(CONFIG_CHROMEOS_LAPTOP) += chromeos_laptop.o
because the left part will resolve to "obj-y" or similar, and you want
to add to it, not replace it. I only changed the Makefile here because
the line was growing too long, and I thought it looked neater this way;
it shouldn't cause any functional change apart from the intended one.
[0] https://www.gnu.org/software/make/manual/html_node/Appending.html
Which makes me think, do we need a Kconfig option for this feature
since not all machines have it?
Not all machines have a lightbar either; both of the features are
runtime-conditional. IMO, it makes more sense this way when you consider
a kernel will likely support multiple platforms.
obj-$(CONFIG_CROS_EC_CHARDEV) += cros_ec_devs.o
obj-$(CONFIG_CROS_EC_LPC) += cros_ec_lpc.o
obj-$(CONFIG_CROS_EC_PROTO) += cros_ec_proto.o
diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c
index e8fcdc2..d19263f 100644
--- a/drivers/platform/chrome/cros_ec_dev.c
+++ b/drivers/platform/chrome/cros_ec_dev.c
@@ -32,6 +32,7 @@ static int ec_major;
static const struct attribute_group *cros_ec_groups[] = {
&cros_ec_attr_group,
&cros_ec_lightbar_attr_group,
+ &cros_ec_vbc_attr_group,
NULL,
};
diff --git a/drivers/platform/chrome/cros_ec_vbc.c b/drivers/platform/chrome/cros_ec_vbc.c
new file mode 100644
index 0000000..a0e8d38
--- /dev/null
+++ b/drivers/platform/chrome/cros_ec_vbc.c
@@ -0,0 +1,137 @@
+/*
+ * cros_ec_vbc - Expose the vboot context nvram to userspace
+ *
+ * Copyright (C) 2015 Collabora Ltd.
+ *
+ * based on vendor driver,
+ *
+ * Copyright (C) 2012 The Chromium OS Authors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/mfd/cros_ec.h>
+#include <linux/mfd/cros_ec_commands.h>
+#include <linux/slab.h>
+
+static ssize_t vboot_context_read(struct file *filp, struct kobject *kobj,
+ struct bin_attribute *att, char *buf,
+ loff_t pos, size_t count)
+{
+ struct device *dev = container_of(kobj, struct device, kobj);
+ struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
+ class_dev);
+ struct cros_ec_device *ecdev = ec->ec_dev;
+ struct ec_params_vbnvcontext *params;
+ struct cros_ec_command *msg;
+ int err;
+ const size_t para_sz = sizeof(struct ec_params_vbnvcontext);
+ const size_t resp_sz = sizeof(struct ec_response_vbnvcontext);
+ const size_t payload = max(para_sz, resp_sz);
+
+ msg = kmalloc(sizeof(*msg) + payload, GFP_KERNEL);
+ if (!msg)
+ return -ENOMEM;
+
+ params = (struct ec_params_vbnvcontext *)msg->data;
+ params->op = EC_VBNV_CONTEXT_OP_READ;
+
+ msg->version = EC_VER_VBNV_CONTEXT;
+ msg->command = EC_CMD_VBNV_CONTEXT;
+ msg->outsize = sizeof(params->op);
Shouldn't this be para_sz ? Since you are sending to the EC the whole
struct ec_params_vbnvcontext and not only the op field.
Or if the EC only expects to get the u32 op field, then I think your
max payload calculation is not correct.
The params struct is the same for both read and write ops, so it has the
op flag and a buffer for the write op. During the read op I believe
there's no need to send this potentially-garbage-filled buffer to the
EC, so outsize is set accordingly here.
The vendor tree does it this way, but I can change it to send the full
buffer if you prefer so.
ec code is at
https://chromium.googlesource.com/chromiumos/platform/ec/+/master/common/system.c
L1086+ if you want to take a look
+ msg->insize = resp_sz;
+
+ err = cros_ec_cmd_xfer(ecdev, msg);
+ if (err < 0) {
+ dev_err(dev, "Error sending read request: %d\n", err);
+ kfree(msg);
+ return err;
+ }
+
+ BUILD_BUG_ON(resp_sz > PAGE_SIZE);
Why you need this? struct ec_response_vbnvcontext is really small AFAICT.
This is just me being paranoid about memcpy :) Indeed, the struct should
be way smaller than a page. I can drop it if you think it's too much.
+ memcpy(buf, msg->data, resp_sz);
+
+ kfree(msg);
+ return resp_sz;
+}
+
Thanks!
Emilio
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/