| Message ID | 1486978066-5351-1-git-send-email-wzz@rock-chips.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
Hi Sean,
Could you give some comments for this patch?
Thanks
Zain
在 2017/2/13 17:27, zain wang 写道:
> 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.
>
> Signed-off-by: zain wang <wzz@rock-chips.com>
> ---
> 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;
> }
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Hi Zain, On Mon, Feb 13, 2017 at 6:27 PM, zain wang <wzz@rock-chips.com> 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@rock-chips.com> > --- > 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. Best regards, Tomasz -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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@rock-chips.com> 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@rock-chips.com> >> --- >> 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 > > > -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Feb 20, 2017 at 1:04 PM, Zain Wang <wzz@rock-chips.com> wrote: > 在 2017/2/20 10:40, Tomasz Figa 写道: >> On Mon, Feb 13, 2017 at 6:27 PM, zain wang <wzz@rock-chips.com> wrote: >>> 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) I think it's still not enough to clean up the code completely. It should be just enough to remove num_transferred completely and simply return msg->size at the end. Best regards, Tomasz -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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; }
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. Signed-off-by: zain wang <wzz@rock-chips.com> --- drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)