On Thu May 22 10:09:55 2025 +0200, Wolfram Sang wrote:
> The HW can only do write-then-read transactions. This is a common
> limitation, so we can add an adapter quirk flag to let the I2C core
> enforce the checks instead of open coding them.
>
> Signed-off-by: Wolfram Sang <wsa+rene...@sang-engineering.com>
> Signed-off-by: Hans Verkuil <hverk...@xs4all.nl>
Patch committed.
Thanks,
Hans Verkuil
drivers/media/usb/hdpvr/hdpvr-i2c.c | 28 ++++------------------------
1 file changed, 4 insertions(+), 24 deletions(-)
---
diff --git a/drivers/media/usb/hdpvr/hdpvr-i2c.c
b/drivers/media/usb/hdpvr/hdpvr-i2c.c
index 54956a8ff15e..9eacc85e3f11 100644
--- a/drivers/media/usb/hdpvr/hdpvr-i2c.c
+++ b/drivers/media/usb/hdpvr/hdpvr-i2c.c
@@ -124,32 +124,12 @@ static int hdpvr_transfer(struct i2c_adapter
*i2c_adapter, struct i2c_msg *msgs,
else
retval = hdpvr_i2c_write(dev, 1, addr, msgs[0].buf,
msgs[0].len);
- } else if (num == 2) {
- if (msgs[0].addr != msgs[1].addr) {
- v4l2_warn(&dev->v4l2_dev, "refusing 2-phase i2c xfer
with conflicting target addresses\n");
- retval = -EINVAL;
- goto out;
- }
-
- if ((msgs[0].flags & I2C_M_RD) || !(msgs[1].flags & I2C_M_RD)) {
- v4l2_warn(&dev->v4l2_dev, "refusing complex xfer with
r0=%d, r1=%d\n",
- msgs[0].flags & I2C_M_RD,
- msgs[1].flags & I2C_M_RD);
- retval = -EINVAL;
- goto out;
- }
-
- /*
- * Write followed by atomic read is the only complex xfer that
- * we actually support here.
- */
+ } else {
+ /* do write-then-read */
retval = hdpvr_i2c_read(dev, 1, addr, msgs[0].buf, msgs[0].len,
msgs[1].buf, msgs[1].len);
- } else {
- v4l2_warn(&dev->v4l2_dev, "refusing %d-phase i2c xfer\n", num);
}
-out:
mutex_unlock(&dev->i2c_mutex);
return retval ? retval : num;
@@ -165,9 +145,9 @@ static const struct i2c_algorithm hdpvr_algo = {
.functionality = hdpvr_functionality,
};
-/* prevent invalid 0-length usb_control_msg */
+/* prevent invalid 0-length usb_control_msg and support only write-then-read */
static const struct i2c_adapter_quirks hdpvr_quirks = {
- .flags = I2C_AQ_NO_ZERO_LEN_READ,
+ .flags = I2C_AQ_NO_ZERO_LEN_READ | I2C_AQ_COMB_WRITE_THEN_READ,
};
static const struct i2c_adapter hdpvr_i2c_adapter_template = {
