Re: [PATCH 05/12] HID: i2c-hid: explicitly code setting and sending reports

From: Dmitry Torokhov
Date: Thu Jan 20 2022 - 01:27:25 EST

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In reply to: Angela Czubak: "Re: [PATCH 05/12] HID: i2c-hid: explicitly code setting and sending reports"
Next in thread: Dmitry Torokhov: "[PATCH 06/12] HID: i2c-hid: define i2c_hid_read_register() and use it"
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Hi Angela,

On Wed, Jan 19, 2022 at 04:31:03PM +0100, Angela Czubak wrote:
> Hi Dmitry,
>
> On Tue, Jan 18, 2022 at 8:26 AM Dmitry Torokhov
> <dmitry.torokhov@xxxxxxxxx> wrote:
> >
> > Instead of relying on __i2c_hid_command() that tries to handle all
> > commands and because of that is very complicated, let's define a
> > new dumb helper i2c_hid_xfer() that actually transfers (write and
> > read) data, and use it when sending and setting reports. By doing
> > that we can save on number of copy operations we have to execute,
> > and make logic of sending reports much clearer.
> >
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> > ---
> > drivers/hid/i2c-hid/i2c-hid-core.c | 269 ++++++++++++++++-------------
> > 1 file changed, 151 insertions(+), 118 deletions(-)
> >
> > diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
> > index 6c1741d9211d..c48b75bd81e0 100644
> > --- a/drivers/hid/i2c-hid/i2c-hid-core.c
> > +++ b/drivers/hid/i2c-hid/i2c-hid-core.c
> > @@ -35,6 +35,7 @@
> > #include <linux/kernel.h>
> > #include <linux/hid.h>
> > #include <linux/mutex.h>
> > +#include <asm/unaligned.h>
> >
> > #include "../hid-ids.h"
> > #include "i2c-hid.h"
> > @@ -47,6 +48,15 @@
> > #define I2C_HID_QUIRK_BAD_INPUT_SIZE BIT(6)
> > #define I2C_HID_QUIRK_NO_WAKEUP_AFTER_RESET BIT(7)
> >
> > +/* Command opcodes */
> > +#define I2C_HID_OPCODE_RESET 0x01
> > +#define I2C_HID_OPCODE_GET_REPORT 0x02
> > +#define I2C_HID_OPCODE_SET_REPORT 0x03
> > +#define I2C_HID_OPCODE_GET_IDLE 0x04
> > +#define I2C_HID_OPCODE_SET_IDLE 0x05
> > +#define I2C_HID_OPCODE_GET_PROTOCOL 0x06
> > +#define I2C_HID_OPCODE_SET_PROTOCOL 0x07
> > +#define I2C_HID_OPCODE_SET_POWER 0x08
> >
> > /* flags */
> > #define I2C_HID_STARTED 0
> > @@ -90,16 +100,6 @@ struct i2c_hid_cmd {
> > unsigned int length;
> > };
> >
> > -union command {
> > - u8 data[0];
> > - struct cmd {
> > - __le16 reg;
> > - __u8 reportTypeID;
> > - __u8 opcode;
> > - __u8 reportID;
> > - } __packed c;
> > -};
> > -
> > #define I2C_HID_CMD(opcode_) \
> > .opcode = opcode_, .length = 4, \
> > .registerIndex = offsetof(struct i2c_hid_desc, wCommandRegister)
> > @@ -115,9 +115,7 @@ static const struct i2c_hid_cmd hid_report_descr_cmd = {
> > /* commands */
> > static const struct i2c_hid_cmd hid_reset_cmd = { I2C_HID_CMD(0x01) };
> > static const struct i2c_hid_cmd hid_get_report_cmd = { I2C_HID_CMD(0x02) };
> > -static const struct i2c_hid_cmd hid_set_report_cmd = { I2C_HID_CMD(0x03) };
> > static const struct i2c_hid_cmd hid_set_power_cmd = { I2C_HID_CMD(0x08) };
> > -static const struct i2c_hid_cmd hid_no_cmd = { .length = 0 };
> >
> > /*
> > * These definitions are not used here, but are defined by the spec.
> > @@ -144,7 +142,6 @@ struct i2c_hid {
> > u8 *inbuf; /* Input buffer */
> > u8 *rawbuf; /* Raw Input buffer */
> > u8 *cmdbuf; /* Command buffer */
> > - u8 *argsbuf; /* Command arguments buffer */
> >
> > unsigned long flags; /* device flags */
> > unsigned long quirks; /* Various quirks */
> > @@ -206,67 +203,90 @@ static u32 i2c_hid_lookup_quirk(const u16 idVendor, const u16 idProduct)
> > return quirks;
> > }
> >
> > +static int i2c_hid_xfer(struct i2c_hid *ihid,
> > + u8 *send_buf, int send_len, u8 *recv_buf, int recv_len)
> > +{
> > + struct i2c_client *client = ihid->client;
> > + struct i2c_msg msgs[2] = { 0 };
> > + int n = 0;
> > + int ret;
> > +
> > + if (send_len) {
> > + i2c_hid_dbg(ihid, "%s: cmd=%*ph\n",
> > + __func__, send_len, send_buf);
> > +
> > + msgs[n].addr = client->addr;
> > + msgs[n].flags = client->flags & I2C_M_TEN;
> > + msgs[n].len = send_len;
> > + msgs[n].buf = send_buf;
> > + n++;
> > + }
> > +
> > + if (recv_len) {
> > + msgs[n].addr = client->addr;
> > + msgs[n].flags = (client->flags & I2C_M_TEN) | I2C_M_RD;
> > + msgs[n].len = recv_len;
> > + msgs[n].buf = recv_buf;
> > + n++;
> > +
> > + set_bit(I2C_HID_READ_PENDING, &ihid->flags);
> > + }
> > +
> > + ret = i2c_transfer(client->adapter, msgs, n);
> > +
> > + if (recv_len)
> > + clear_bit(I2C_HID_READ_PENDING, &ihid->flags);
> > +
> > + if (ret != n)
> > + return ret < 0 ? ret : -EIO;
> > +
> > + return 0;
> > +}
> > +
> > +static size_t i2c_hid_encode_command(u8 *buf, u8 opcode,
> > + int report_type, int report_id)
>
> Can it ever be used to encode something else than the command register?
> If not, perhaps we could fill it here as well.

It indeed always called after setting command register, however I
believe the register and command are logically distinct entities and
that it why I prefer not to handle the register here.

>
> > +{
> > + size_t length = 0;
> > +
> > + if (report_id < 0x0F) {
> > + buf[length++] = report_type << 4 | report_id;
> > + buf[length++] = opcode;
> > + } else {
> > + buf[length++] = report_type << 4 | 0x0F;
> > + buf[length++] = opcode;
> > + buf[length++] = report_id;
> > + }
> > +
> > + return length;
> > +}
> > +
> > static int __i2c_hid_command(struct i2c_hid *ihid,
> > const struct i2c_hid_cmd *command, u8 reportID,
> > u8 reportType, u8 *args, int args_len,
> > unsigned char *buf_recv, int data_len)
> > {
> > - struct i2c_client *client = ihid->client;
> > - union command *cmd = (union command *)ihid->cmdbuf;
> > - int ret;
> > - struct i2c_msg msg[2];
> > - int msg_num = 1;
> > -
> > int length = command->length;
> > unsigned int registerIndex = command->registerIndex;
> >
> > /* special case for hid_descr_cmd */
> > if (command == &hid_descr_cmd) {
> > - cmd->c.reg = ihid->wHIDDescRegister;
> > + *(__le16 *)ihid->cmdbuf = ihid->wHIDDescRegister;
> > } else {
> > - cmd->data[0] = ihid->hdesc_buffer[registerIndex];
> > - cmd->data[1] = ihid->hdesc_buffer[registerIndex + 1];
> > + ihid->cmdbuf[0] = ihid->hdesc_buffer[registerIndex];
> > + ihid->cmdbuf[1] = ihid->hdesc_buffer[registerIndex + 1];
> > }
> >
> > if (length > 2) {
> > - cmd->c.opcode = command->opcode;
> > - if (reportID < 0x0F) {
> > - cmd->c.reportTypeID = reportType << 4 | reportID;
> > - } else {
> > - cmd->c.reportTypeID = reportType << 4 | 0x0F;
> > - cmd->c.reportID = reportID;
> > - length++;
> > - }
> > + length = sizeof(__le16) + /* register */
> > + i2c_hid_encode_command(ihid->cmdbuf + sizeof(__le16),
> > + command->opcode,
> > + reportType, reportID);
> > }
> >
> > - memcpy(cmd->data + length, args, args_len);
> > + memcpy(ihid->cmdbuf + length, args, args_len);
> > length += args_len;
> >
> > - i2c_hid_dbg(ihid, "%s: cmd=%*ph\n", __func__, length, cmd->data);
> > -
> > - msg[0].addr = client->addr;
> > - msg[0].flags = client->flags & I2C_M_TEN;
> > - msg[0].len = length;
> > - msg[0].buf = cmd->data;
> > - if (data_len > 0) {
> > - msg[1].addr = client->addr;
> > - msg[1].flags = client->flags & I2C_M_TEN;
> > - msg[1].flags |= I2C_M_RD;
> > - msg[1].len = data_len;
> > - msg[1].buf = buf_recv;
> > - msg_num = 2;
> > - set_bit(I2C_HID_READ_PENDING, &ihid->flags);
> > - }
> > -
> > - ret = i2c_transfer(client->adapter, msg, msg_num);
> > -
> > - if (data_len > 0)
> > - clear_bit(I2C_HID_READ_PENDING, &ihid->flags);
> > -
> > - if (ret != msg_num)
> > - return ret < 0 ? ret : -EIO;
> > -
> > - return 0;
> > + return i2c_hid_xfer(ihid, ihid->cmdbuf, length, buf_recv, data_len);
> > }
> >
> > static int i2c_hid_command(struct i2c_hid *ihid,
> > @@ -301,70 +321,81 @@ static int i2c_hid_get_report(struct i2c_hid *ihid, u8 reportType,
> > return 0;
> > }
> >
> > +static size_t i2c_hid_format_report(u8 *buf, int report_id,
> > + const u8 *data, size_t size)
> > +{
> > + size_t length = sizeof(__le16); /* reserve space to store size */
> > +
> > + if (report_id)
> > + buf[length++] = report_id;
> > +
> > + memcpy(buf + length, data, size);
> > + length += size;
> > +
> > + /* Store overall size in the beginning of the buffer */
> > + put_unaligned_le16(length, buf);
> > +
> > + return length;
> > +}
> > +
> > /**
> > * i2c_hid_set_or_send_report: forward an incoming report to the device
> > * @ihid: the i2c hid device
> > - * @reportType: 0x03 for HID_FEATURE_REPORT ; 0x02 for HID_OUTPUT_REPORT
> > - * @reportID: the report ID
> > + * @report_type: 0x03 for HID_FEATURE_REPORT ; 0x02 for HID_OUTPUT_REPORT
> > + * @report_id: the report ID
> > * @buf: the actual data to transfer, without the report ID
> > * @data_len: size of buf
> > - * @use_data: true: use SET_REPORT HID command, false: send plain OUTPUT report
> > + * @do_set: true: use SET_REPORT HID command, false: send plain OUTPUT report
> > */
> > -static int i2c_hid_set_or_send_report(struct i2c_hid *ihid, u8 reportType,
> > - u8 reportID, unsigned char *buf, size_t data_len, bool use_data)
> > +static int i2c_hid_set_or_send_report(struct i2c_hid *ihid,
> > + u8 report_type, u8 report_id,
> > + const u8 *buf, size_t data_len,
> > + bool do_set)
> > {
> > - u8 *args = ihid->argsbuf;
> > - const struct i2c_hid_cmd *hidcmd;
> > - int ret;
> > - u16 dataRegister = le16_to_cpu(ihid->hdesc.wDataRegister);
> > - u16 outputRegister = le16_to_cpu(ihid->hdesc.wOutputRegister);
> > - u16 maxOutputLength = le16_to_cpu(ihid->hdesc.wMaxOutputLength);
> > - u16 size;
> > - int args_len;
> > - int index = 0;
> > + size_t length = 0;
> > + int error;
> >
> > i2c_hid_dbg(ihid, "%s\n", __func__);
> >
> > if (data_len > ihid->bufsize)
> > return -EINVAL;
> >
> > - size = 2 /* size */ +
> > - (reportID ? 1 : 0) /* reportID */ +
> > - data_len /* buf */;
> > - args_len = 2 /* dataRegister */ +
> > - size /* args */;
> > -
> > - if (!use_data && maxOutputLength == 0)
> > + if (!do_set && le16_to_cpu(ihid->hdesc.wMaxOutputLength) == 0)
> > return -ENOSYS;
> >
> > - /*
> > - * use the data register for feature reports or if the device does not
> > - * support the output register
> > - */
> > - if (use_data) {
> > - args[index++] = dataRegister & 0xFF;
> > - args[index++] = dataRegister >> 8;
> > - hidcmd = &hid_set_report_cmd;
> > + if (do_set) {
> > + /* Command register goes first */
> > + *(__le16 *)ihid->cmdbuf = ihid->hdesc.wCommandRegister;
> > + length += sizeof(__le16);
> > + /* Next is SET_REPORT command */
> > + length += i2c_hid_encode_command(ihid->cmdbuf + length,
> > + I2C_HID_OPCODE_SET_REPORT,
> > + report_type, report_id);
> > + /*
> > + * Report data will go into the data register. Because
> > + * command can be either 2 or 3 bytes destination for
> > + * the data register may be not aligned.
> > + */
> > + put_unaligned_le16(le16_to_cpu(ihid->hdesc.wDataRegister),
> > + ihid->cmdbuf + length);
> > + length += sizeof(__le16);
> > } else {
> > - args[index++] = outputRegister & 0xFF;
> > - args[index++] = outputRegister >> 8;
> > - hidcmd = &hid_no_cmd;
> > + /*
> > + * With simple "send report" all data goes into the output
> > + * register.
> > + */
> > + *(__le16 *)ihid->cmdbuf = ihid->hdesc.wCommandRegister;
>
> I believe you meant ' *(__le16 *)ihid->cmdbuf = ihid->hdesc.wOutputRegister;' :)

Yes, indeed. Thank you for spotting this!

--
Dmitry

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