diff mbox

[v1,2/2] drm/bridge/synopsys: dsi: Add a warning msg on dsi read operations

Message ID 20180123142618.28384-3-philippe.cornu@st.com (mailing list archive)
State New, archived
Headers show

Commit Message

Philippe CORNU Jan. 23, 2018, 2:26 p.m. UTC
The DCS/GENERIC DSI read feature is not yet implemented so it
is important to warn the host_transfer() caller in case of
read operation requests.

Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
---
 drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

Comments

Brian Norris Jan. 23, 2018, 9:28 p.m. UTC | #1
Hi Philippe,

I see you sent this out already today, while I only just responded
(late) to your questions about it... oh well :)

On Tue, Jan 23, 2018 at 6:26 AM, Philippe Cornu <philippe.cornu@st.com> wrote:
> The DCS/GENERIC DSI read feature is not yet implemented so it
> is important to warn the host_transfer() caller in case of
> read operation requests.
>
> Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> index 096cf5e5bb30..e46ddff8601c 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> @@ -417,7 +417,14 @@ static ssize_t dw_mipi_dsi_host_transfer(struct mipi_dsi_host *host,
>         if (ret)
>                 return ret;
>
> -       nb_bytes = packet.size;
> +       if (msg->rx_buf && msg->rx_len > 0) {

It feels like you should do this check *before* you start writing
anything. It's possible to have a combination TX/RX command, and it
would be counterintuitive to only do half the operation then return
with an argument error.

> +               /* TODO dw drv improvements: implement read feature */
> +               dev_warn(dsi->dev, "read operations not yet implemented\n");
> +               return -EPERM;

I'm not sure -EPERM is right. Feels like -EINVAL, -ENOSYS, or
-EOPNOTSUPP. I think -ENOSYS actually has been abused somewhat, so
maybe one of the other two.

> +

Spurious blank line?

> +       } else {
> +               nb_bytes = packet.size;
> +       }

You don't actually need to put this sort of thing in the 'else' case.
The other branch is an error-handling case, which definitely 'return's
early, and it's pretty standard coding style to avoid indenting the
"good" path like this.

Brian

>
>         return nb_bytes;
>  }
> --
> 2.15.1
>
Philippe CORNU Jan. 24, 2018, 1:22 p.m. UTC | #2
Hi Brian,


On 01/23/2018 10:28 PM, Brian Norris wrote:
> Hi Philippe,
> 
> I see you sent this out already today, while I only just responded
> (late) to your questions about it... oh well :)
> 

I got a short period to clean-up and adds features to this driver (1.31 
ip version + maybe the read feature), sorry to have not wait a single 
day more.

> On Tue, Jan 23, 2018 at 6:26 AM, Philippe Cornu <philippe.cornu@st.com> wrote:
>> The DCS/GENERIC DSI read feature is not yet implemented so it
>> is important to warn the host_transfer() caller in case of
>> read operation requests.
>>
>> Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
>> ---
>>   drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 9 ++++++++-
>>   1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> index 096cf5e5bb30..e46ddff8601c 100644
>> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> @@ -417,7 +417,14 @@ static ssize_t dw_mipi_dsi_host_transfer(struct mipi_dsi_host *host,
>>          if (ret)
>>                  return ret;
>>
>> -       nb_bytes = packet.size;
>> +       if (msg->rx_buf && msg->rx_len > 0) {
> 
> It feels like you should do this check *before* you start writing
> anything. It's possible to have a combination TX/RX command, and it
> would be counterintuitive to only do half the operation then return
> with an argument error.
> 

Many thanks for your review.

I agree with your comments.

Well, my patch is not good at all because it contains a small part of 
the read feature I am writing... but it is not the purpose of this patch.

No excuse, sorry guys for making you waste time.

I will re-write a new patch 100% decorrelated from a possible future 
read feature.

I could also wait until I have a working read feature but as it could 
take some times, I prefer warning users asap.

>> +               /* TODO dw drv improvements: implement read feature */
>> +               dev_warn(dsi->dev, "read operations not yet implemented\n");
>> +               return -EPERM;
> 
> I'm not sure -EPERM is right. Feels like -EINVAL, -ENOSYS, or
> -EOPNOTSUPP. I think -ENOSYS actually has been abused somewhat, so
> maybe one of the other two.
> 

not easy to pick the right one. I will use -EINVAL.

>> +
> 
> Spurious blank line?
> 
thanks

>> +       } else {
>> +               nb_bytes = packet.size;
>> +       }
> 
> You don't actually need to put this sort of thing in the 'else' case.
> The other branch is an error-handling case, which definitely 'return's
> early, and it's pretty standard coding style to avoid indenting the
> "good" path like this.
> 
> Brian
> 

The else part is linked to my "read feature" too, sorry for that. I will 
do it simpler in next version.

Thank you,
Philippe :-)

>>
>>          return nb_bytes;
>>   }
>> --
>> 2.15.1
>>
Brian Norris Jan. 24, 2018, 6:14 p.m. UTC | #3
Hi Philippe,

On Wed, Jan 24, 2018 at 01:22:04PM +0000, Philippe CORNU wrote:
> On 01/23/2018 10:28 PM, Brian Norris wrote:
> > I see you sent this out already today, while I only just responded
> > (late) to your questions about it... oh well :)
> > 
> 
> I got a short period to clean-up and adds features to this driver (1.31 
> ip version + maybe the read feature), sorry to have not wait a single 
> day more.

No problem. The key word was "late"; my mail was buried enough I just
missed responding. Not your fault!

> > On Tue, Jan 23, 2018 at 6:26 AM, Philippe Cornu <philippe.cornu@st.com> wrote:
> >> The DCS/GENERIC DSI read feature is not yet implemented so it
> >> is important to warn the host_transfer() caller in case of
> >> read operation requests.
> >>
> >> Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
> >> ---
> >>   drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 9 ++++++++-
> >>   1 file changed, 8 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> >> index 096cf5e5bb30..e46ddff8601c 100644
> >> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> >> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> >> @@ -417,7 +417,14 @@ static ssize_t dw_mipi_dsi_host_transfer(struct mipi_dsi_host *host,
> >>          if (ret)
> >>                  return ret;
> >>
> >> -       nb_bytes = packet.size;
> >> +       if (msg->rx_buf && msg->rx_len > 0) {
> > 
> > It feels like you should do this check *before* you start writing
> > anything. It's possible to have a combination TX/RX command, and it
> > would be counterintuitive to only do half the operation then return
> > with an argument error.
> > 
> 
> Many thanks for your review.
> 
> I agree with your comments.
> 
> Well, my patch is not good at all because it contains a small part of 
> the read feature I am writing... but it is not the purpose of this patch.
> 
> No excuse, sorry guys for making you waste time.

No worries. These weren't that bad anyway, just a little suboptimal :)

> I will re-write a new patch 100% decorrelated from a possible future 
> read feature.

Yeah, that would probably work best. It's hard to write and review good
"intermediate" code; we should write it as if the code will last as-is.

> I could also wait until I have a working read feature but as it could 
> take some times, I prefer warning users asap.

Sounds good.

[snip]

Thanks,
Brian
diff mbox

Patch

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
index 096cf5e5bb30..e46ddff8601c 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
@@ -417,7 +417,14 @@  static ssize_t dw_mipi_dsi_host_transfer(struct mipi_dsi_host *host,
 	if (ret)
 		return ret;
 
-	nb_bytes = packet.size;
+	if (msg->rx_buf && msg->rx_len > 0) {
+		/* TODO dw drv improvements: implement read feature */
+		dev_warn(dsi->dev, "read operations not yet implemented\n");
+		return -EPERM;
+
+	} else {
+		nb_bytes = packet.size;
+	}
 
 	return nb_bytes;
 }