Re: [PATCH 18/18] HID: i2c-hid: fix i2c_hid_set_or_send_report

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

Hi Angela,

On Tue, Dec 21, 2021 at 07:17:43PM +0000, Angela Czubak wrote:
> If command & data registers are to be used and report ID >= 0xF
> use the sentinel value for report ID in the command.
> Do not alter the report ID itself as it needs to be inserted into the args
> buffer. If output register is to be used there is no need to insert
> report IDs >= 0xF.

OK, I see what you mean, but I believe that i2c_hid_set_or_send_report()
is the wrong place to implement this handling to begin with. How about a
modified version of your patch that I am pasting below (not tested)?

Thanks,
Dmitry

-- >8 -- >8 --


HID: i2c-hid: fix handling numbered reports with IDs of 15 and above

From: Angela Czubak <acz@semihalf.com>

Special handling of numbered reports with IDs of 15 and above is only
needed when executing what HID-I2C spec is calling "Class Specific
Requests", and not when simply sending output reports.

Additionally, our mangling of report ID in i2c_hid_set_or_send_report()
resulted in incorrect report ID being written into SET_REPORT command
payload.

To solve it let's move all the report ID manipulation into
__i2c_hid_command() where we form the command data structure.

Signed-off-by: Angela Czubak <acz@semihalf.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/hid/i2c-hid/i2c-hid-core.c |   22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
index 517141138b00..9381a70b2948 100644
--- a/drivers/hid/i2c-hid/i2c-hid-core.c
+++ b/drivers/hid/i2c-hid/i2c-hid-core.c
@@ -97,6 +97,7 @@ union command {
 		__le16 reg;
 		__u8 reportTypeID;
 		__u8 opcode;
+		__u8 reportID;
 	} __packed c;
 };
 
@@ -232,7 +233,13 @@ static int __i2c_hid_command(struct i2c_client *client,
 
 	if (length > 2) {
 		cmd->c.opcode = command->opcode;
-		cmd->c.reportTypeID = reportID | reportType << 4;
+		if (reportID < 0x0F) {
+			cmd->c.reportTypeID = reportType << 4 | reportID;
+		} else {
+			cmd->c.reportTypeID = reportType << 4 | 0x0F;
+			cmd->c.reportID = reportID;
+			length++;
+		}
 	}
 
 	memcpy(cmd->data + length, args, args_len);
@@ -300,11 +307,6 @@ static int i2c_hid_get_report(struct i2c_client *client, u8 reportType,
 
 	i2c_hid_dbg(ihid, "%s\n", __func__);
 
-	if (reportID >= 0x0F) {
-		args[args_len++] = reportID;
-		reportID = 0x0F;
-	}
-
 	args[args_len++] = readRegister & 0xFF;
 	args[args_len++] = readRegister >> 8;
 
@@ -350,18 +352,12 @@ static int i2c_hid_set_or_send_report(struct i2c_client *client, u8 reportType,
 	size =		2			/* size */ +
 			(reportID ? 1 : 0)	/* reportID */ +
 			data_len		/* buf */;
-	args_len =	(reportID >= 0x0F ? 1 : 0) /* optional third byte */ +
-			2			/* dataRegister */ +
+	args_len =	2			/* dataRegister */ +
 			size			/* args */;
 
 	if (!use_data && maxOutputLength == 0)
 		return -ENOSYS;
 
-	if (reportID >= 0x0F) {
-		args[index++] = reportID;
-		reportID = 0x0F;
-	}
-
 	/*
 	 * use the data register for feature reports or if the device does not
 	 * support the output register