[PATCH v7 6/9] drm/simpledrm: Add drm_panic support

[Thomas Zimmermann]

Hi

Am 12.01.24 um 14:58 schrieb Maxime Ripard:
> On Fri, Jan 12, 2024 at 02:44:57PM +0100, Daniel Vetter wrote:
>> On Thu, Jan 04, 2024 at 05:00:50PM +0100, Jocelyn Falempe wrote:
>>> Add support for the drm_panic module, which displays a user-friendly
>>> message to the screen when a kernel panic occurs.
>>>
>>> Signed-off-by: Jocelyn Falempe <jfalempe at redhat.com>
>>> ---
>>>   drivers/gpu/drm/tiny/simpledrm.c | 15 +++++++++++++++
>>>   1 file changed, 15 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
>>> index 7ce1c4617675..6dd2afee84d4 100644
>>> --- a/drivers/gpu/drm/tiny/simpledrm.c
>>> +++ b/drivers/gpu/drm/tiny/simpledrm.c
>>> @@ -25,6 +25,7 @@
>>>   #include <drm/drm_gem_shmem_helper.h>
>>>   #include <drm/drm_managed.h>
>>>   #include <drm/drm_modeset_helper_vtables.h>
>>> +#include <drm/drm_panic.h>
>>>   #include <drm/drm_probe_helper.h>
>>>   
>>>   #define DRIVER_NAME	"simpledrm"
>>> @@ -985,6 +986,19 @@ static struct simpledrm_device *simpledrm_device_create(struct drm_driver *drv,
>>>   	return sdev;
>>>   }
>>>   
>>> +static int simpledrm_get_scanout_buffer(struct drm_device *dev,
>>> +					struct drm_scanout_buffer *sb)
>>> +{
>>> +	struct simpledrm_device *sdev = simpledrm_device_of_dev(dev);
>>
>> So I guess simpledrm is the reason why the get_scanout_buffer hook is at
>> the device level and not at the plane level. Even from the few drivers you
>> have in your series it seems very much the exception, so I'm not sure
>> whether that's the best design.
>>
>> I guess we'll know when we see the plane iterator code with the right
>> locking, whether it's ok to have that in driver hooks or it's better to
>> pull it out into shared code.
> 
> Wouldn't the CRTC level be better than the planes?

What's in favor of the CRTC level?

I'd put a hook at the plane level and do the 
drm_for_each_primary_visible_plane() in the panic handler. Simpledrm 
would fit into this pattern nicely.

But it's not like I have strong feeling about this. The current 
callbacks are simple enough.

Best regards
Thomas

> 
> Maxime

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
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