[PATCH] drm: don't call ->firstopen for KMS drivers

[Daniel Vetter]

On Thu, Jul 11, 2013 at 9:54 AM, Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
> Hi Daniel,
>
> On Wednesday 10 July 2013 20:17:44 Daniel Vetter wrote:
>> It has way too much potential for driver writers to do stupid things
>> like delayed hw setup because the load sequence is somehow racy (e.g.
>> the imx driver in staging). So don't call it for modesetting drivers,
>> which reduces the complexity of the drm core -> driver interface a
>> notch.
>>
>> v2: Don't forget to update DocBook.
>>
>> Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>> ---
>>  Documentation/DocBook/drm.tmpl | 2 ++
>>  drivers/gpu/drm/drm_fops.c     | 3 ++-
>>  2 files changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
>> index 4d54ac8..0e8a5a3 100644
>> --- a/Documentation/DocBook/drm.tmpl
>> +++ b/Documentation/DocBook/drm.tmpl
>> @@ -2423,6 +2423,8 @@ void (*postclose) (struct drm_device *, struct
>> drm_file *);</synopsis> <para>
>>          The <methodname>firstopen</methodname> method is called by the DRM
>> core when an application opens a device that has no other opened file
>> handle.
>> +     Not that this callback is only called for legacy ums drm drivers, not
>> +     for drm drivers that implement modesetting in the kernel.
>>       Similarly the <methodname>lastclose</methodname> method is called when
>>       the last application holding a file handle opened on the device closes
>>       it. Both methods are mostly used for UMS (User Mode Setting) drivers to
>
> What about

So if you think we should go overboard I guess it'd be useful to
explain what KMS drivers should and shouldn't do in lastclose:
- Delayed gpu switching with vga switcheroo.
- Restoring of the fbcon, as long as the core is still a bit deficient
in getting rid of mouse cursors and stupid sprite setups when X dies
untimely and leaves dirt behind. Eventually we should be able to get
rid of this though and rely on the magic sysrq to get out of graphics
mode and restore fbcon fully.
- Nothing else, ever, especially resource cleanups.

Can you maybe add a sentence or two to your proposed update for about
this? UMS drivers tend to do a lot of nefarious stuff in lastclose, so
stressing the difference would be good.

Otherwise I like your doc update much more than mine ;-)
-Daniel

>
> diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
> index 7d1278e..afa8d40 100644
> --- a/Documentation/DocBook/drm.tmpl
> +++ b/Documentation/DocBook/drm.tmpl
> @@ -2422,18 +2422,18 @@ void (*postclose) (struct drm_device *, struct drm_file *);</synopsis>
>        </abstract>
>        <para>
>          The <methodname>firstopen</methodname> method is called by the DRM core
> -       when an application opens a device that has no other opened file handle.
> -       Similarly the <methodname>lastclose</methodname> method is called when
> -       the last application holding a file handle opened on the device closes
> -       it. Both methods are mostly used for UMS (User Mode Setting) drivers to
> -       acquire and release device resources which should be done in the
> -       <methodname>load</methodname> and <methodname>unload</methodname>
> -       methods for KMS drivers.
> +       for legacy UMS (User Mode Setting) drivers only when an application
> +       opens a device that has no other opened file handle. UMS drivers can
> +       implement it to acquire device resources. KMS drivers can't use the
> +       method and must acquire resources in the <methodname>load</methodname>
> +       method instead.
>        </para>
>        <para>
> -        Note that the <methodname>lastclose</methodname> method is also called
> -       at module unload time or, for hot-pluggable devices, when the device is
> -       unplugged. The <methodname>firstopen</methodname> and
> +       Similarly the <methodname>lastclose</methodname> method is called when
> +       the last application holding a file handle opened on the device closes
> +       it, for both UMS and KMS drivers. Additionally, the method is also
> +       called at module unload time or, for hot-pluggable devices, when the
> +       device is unplugged. The <methodname>firstopen</methodname> and
>         <methodname>lastclose</methodname> calls can thus be unbalanced.
>        </para>
>        <para>
>
>> diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
>> index 57e3014..fcde7d4 100644
>> --- a/drivers/gpu/drm/drm_fops.c
>> +++ b/drivers/gpu/drm/drm_fops.c
>> @@ -51,7 +51,8 @@ static int drm_setup(struct drm_device * dev)
>>       int i;
>>       int ret;
>>
>> -     if (dev->driver->firstopen) {
>> +     if (dev->driver->firstopen &&
>> +         !drm_core_check_feature(dev, DRIVER_MODESET)) {
>>               ret = dev->driver->firstopen(dev);
>>               if (ret != 0)
>>                       return ret;
>
> --
> Regards,
>
> Laurent Pinchart



--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch