Hi Javier Am 10.05.22 um 11:06 schrieb Javier Martinez Canillas:
Hello Thomas, On 5/10/22 10:50, Thomas Zimmermann wrote: [snip]Drivers shouldn't really explicitly call this helper in my opinion.One more stupid question: does armada actually use drm_fbdev_fb_destroy()? It's supposed to be a callback for struct fb_ops. Armada uses it's own instance of fb_ops, which apparently doesn't contain fb_destroy. [1]No stupid question at all. You are correct on this. So I guess we still need this call in the drivers that don't provide a .fb_destroy() handler. I see many options here: 1) Document in drm_fb_helper_alloc_fbi() that drivers only need to call drm_fb_helper_fini() explicitly if they are not setting up a fbdev with drm_fbdev_generic_setup(), otherwise is not needed. 2) Make drm_fbdev_fb_destroy() an exported symbol so drivers that have custom fb_ops can use it. 3) Set .fb_destroy to drm_fbdev_fb_destroy() if isn't set by drivers when they call drm_fb_helper_initial_config() or drm_fb_helper_fill_info(). I'm leaning towards option (3). Then the fb_info release will be automatic whether drivers are using the generic setup or a custom one.
IMHO this would just be another glitch to paper over all the broken code. And if you follow through drm_fbdev_fb_helper(), [1] it'll call _fini at some point and probably blow up in some other way. Instances of struct fb_ops are also usually const.
The only reliable way AFAICT is to do what generic fbdev does: use unregister_framebuffer and do the software cleanup somewhere within fb_destroy. And then fix all drivers to use that pattern.
Best regards Thomas[1] https://elixir.bootlin.com/linux/v5.17.6/source/drivers/gpu/drm/drm_fb_helper.c#L2082
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev
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