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2024-01-30soc: apple: mailbox: error pointers are negative integersLinus Torvalds
In an entirely unrelated discussion where I pointed out a stupid thinko of mine, Rasmus piped up and noted that that obvious mistake already existed elsewhere in the kernel tree. An "error pointer" is the negative error value encoded as a pointer, making the whole "return error or valid pointer" use-case simple and straightforward. We use it all over the kernel. But the key here is that errors are _negative_ error numbers, not the horrid UNIX user-level model of "-1 and the value of 'errno'". The Apple mailbox driver used the positive error values, and thus just returned invalid normal pointers instead of actual errors. Of course, the reason nobody ever noticed is that the errors presumably never actually happen, so this is fixing a conceptual bug rather than an actual one. Reported-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk> Link: https://lore.kernel.org/all/5c30afe0-f9fb-45d5-9333-dd914a1ea93a@prevas.dk/ Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-11-23soc: apple: mailbox: Add explicit include of platform_device.hRob Herring
The DT of_device.h and of_platform.h date back to the separate of_platform_bus_type before it as merged into the regular platform bus. As part of that merge prepping Arm DT support 13 years ago, they "temporarily" include each other and pull in various other headers. In preparation to fix this, adjust the includes for what is actually needed. platform_device.h is implicitly included by of_platform.h, but that's going to be removed. Signed-off-by: Rob Herring <robh@kernel.org> Reviewed-by: Neal Gompa <neal@gompa.dev> Signed-off-by: Hector Martin <marcan@marcan.st>
2023-11-23soc: apple: mailbox: Add ASC/M3 mailbox driverHector Martin
This new driver is based on the existing apple-mailbox driver, but replaces the usage of the mailbox subsystem with directly exported symbols. As part of this refactor, this adds support for using the hardware FIFOs (not supported in mailbox) and implicitly fixes a bunch of bugs caused by bad interactions with the mailbox subsystem. It also adds runtime-PM support. The new config symbol is APPLE_MBOX, while the module name remains identical ("apple-mailbox"). The configs are mutually exclusive in Kconfig, to avoid conflicts. Acked-by: Eric Curtin <ecurtin@redhat.com> Acked-by: Neal Gompa <neal@gompa.dev> Acked-by: Alyssa Rosenzweig <alyssa@rosenzweig.io> Signed-off-by: Hector Martin <marcan@marcan.st>