Re: [PATCH] drm/bridge: analogix_dp: Don't return -EBUSY when msg->size is 0 in aux transaction

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi Tomasz,

在 2017/2/20 10:40, Tomasz Figa 写道:
Hi Zain,

On Mon, Feb 13, 2017 at 6:27 PM, zain wang <wzz@xxxxxxxxxxxxxx> wrote:
The analogix_dp_transfer() will return -EBUSY if num_transferred is zero.
But sometimes we will send a bare address packet to start the transaction,
like drm_dp_i2c_xfer() show:
         ......
         /* Send a bare address packet to start the transaction.
          * Zero sized messages specify an address only (bare
          * address) transaction.
          */
         msg.buffer = NULL;
         msg.size = 0;
         err = drm_dp_i2c_do_msg(aux, &msg);
         ......

In this case, the msg->size is zero, so the num_transferred will be zero too.
We can't return -EBUSY here, let's we return num_transferred if num_transferred
equals msg->size.

Please see my question inline.

Signed-off-by: zain wang <wzz@xxxxxxxxxxxxxx>
---
  drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
index 303083a..5384aca 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
@@ -1162,5 +1162,5 @@ ssize_t analogix_dp_transfer(struct analogix_dp_device *dp,
                  (msg->request & ~DP_AUX_I2C_MOT) == DP_AUX_NATIVE_READ)
                 msg->reply = DP_AUX_NATIVE_REPLY_ACK;

-       return num_transferred > 0 ? num_transferred : -EBUSY;
+       return (num_transferred == msg->size) ? num_transferred : -EBUSY;
I might be missing something but, looking at the code, I don't see any
possibility of num_transferred ever being different than msg->size. To
be honest, it doesn't seem to even make any sense keeping the local
variable there, because msg->size can be simply always returned, as
errors are handled by jumping to aux_error label.
Yeah, I agree with you.
The better way to fix this issue is to revert the changes https://patchwork.kernel.org/patch/9411711/
(returning num_transferred directly may be better here)

Maybe we can revert the changes above with some new comment.
@Sean, How do you think about Tomasz's comment?

Thanks
Zain

Best regards,
Tomasz





_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel




[Index of Archives]     [Linux DRI Users]     [Linux Intel Graphics]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux