Hi Sam Am 31.07.21 um 20:50 schrieb Sam Ravnborg:
Hi Thomas, On Tue, Jul 27, 2021 at 08:27:07PM +0200, Thomas Zimmermann wrote:DRM's IRQ helpers are only helpful for old, non-KMS drivers. Move the code behind CONFIG_DRM_LEGACY. Convert KMS drivers to Linux IRQ interfaces. DRM provides IRQ helpers for setting up, receiving and removing IRQ handlers. It's an abstraction over plain Linux functions. The code is mid-layerish with several callbacks to hook into the rsp drivers. Old UMS driver have their interrupts enabled via ioctl, so these abstractions makes some sense. Modern KMS manage all their interrupts internally. Using the DRM helpers adds indirection without benefits. Most KMs drivers already use Linux IRQ functions instead of DRM's abstraction layer. Patches 1 to 12 convert the remaining ones. The patches also resolve a bug for devices without assigned interrupt number. DRM helpers don't test for IRQ_NOTCONNECTED, so drivers do not detect if the device has no interrupt assigned. Patch 13 removes an unused function. Patch 14 moves the DRM IRQ helpers behind CONFIG_DRM_LEGACY. Only the old non-KMS drivers still use the functionality. Thomas Zimmermann (14): drm/amdgpu: Convert to Linux IRQ interfaces drm/arm/hdlcd: Convert to Linux IRQ interfaces drm/atmel-hlcdc: Convert to Linux IRQ interfaces drm/fsl-dcu: Convert to Linux IRQ interfaces drm/gma500: Convert to Linux IRQ interfaces drm/kmb: Convert to Linux IRQ interfaces drm/msm: Convert to Linux IRQ interfaces drm/mxsfb: Convert to Linux IRQ interfaces drm/radeon: Convert to Linux IRQ interfaces drm/tidss: Convert to Linux IRQ interfaces drm/tilcdc: Convert to Linux IRQ interfaces drm/vc4: Convert to Linux IRQ interfaces drm: Remove unused devm_drm_irq_install() drm: IRQ midlayer is now legacyWith the irq_enabled confusion out of the way I want to re-address two issues here that I know you have answered but I am just not convinced. 1) IRQ_NOTCONNECTED We do not have this check in drm_irq today and we should avoid spreading it all over. We are either carrying it forever or we wil lsee patches floating in to drop the check again. The current use in the kernel is minimal: https://elixir.bootlin.com/linux/latest/A/ident/IRQ_NOTCONNECTED So as a minimum drop it from atmel_hlcdc and preferably from the rest as it is really not used. (Speaking as atmel_hlcdc maintainer)
I'll drop it from atmel_hlcdc then.But saying that it's not used is not correct. At least radeon an gma500 handle PCI-based devices and BIOSes often had the option of disabling the rsp graphics interrupts.
2) devm_request_irq() We are moving towards managed allocation so we do not fail to free resources. And an irq has a lifetime equal the device itself - so an obvious cnadidate for devm_request_irq. If we do not introduce it now we will see a revisit of this later. I can be convinced to wait with this as we will have to do much more in each driver, but I cannot see any good arguments to avoid the more modern way to use devm_request_irq.
I'll change this in atmel_hdlcd and maybe I can find trivial cases where devm_request_irq() can be used. But drivers that had an uninstall callback before should not have the cleanup logic altered by a patch as this one. I suspect that most of the IRQ cleanup is actually a vblank cleanup and should be done in response to drm_vblank_init(). But that's again not something for this patchset here. We cannot change multiple things at once and still expect any of it to work.
I welcome the use of devm_ et al. But these changes are better done in a per-driver patchset that changes all of the driver to managed release.
Best regards Thomas
Sam
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Felix Imendörffer
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