Re: [06/12] arch: Declare screen_info in <asm/screen_info.h>

Hi,


Why this patch get dropped in the end?

Since the global screen_info is an arch-specific thing,
Whenever an arch-neutral module or subsystem references the global screen_info,
There are some complaints from either compile testing robot.
Well, a programmer may handle it by using the CONFIG_SYSFB guard,
but it is not as precise as what this patch provided.

Personally, I think this patch is still valuable.
I suggest either forcing all other architectures to export screen_info,
like the X86 and IA64 arch does, after all the screen_info is a good thing.
or provide the fine-control version like this patch does.


On 2023/6/29 19:45, Thomas Zimmermann wrote:
> The variable screen_info does not exist on all architectures. Declare
> it in <asm-generic/screen_info.h>. All architectures that do declare it
> will provide it via <asm/screen_info.h>.
>
> Add the Kconfig token ARCH_HAS_SCREEN_INFO to guard against access on
> architectures that don't provide screen_info.
>
> Signed-off-by: Thomas Zimmermann <[email protected]>
> Cc: Richard Henderson <[email protected]>
> Cc: Ivan Kokshaysky <[email protected]>
> Cc: Matt Turner <[email protected]>
> Cc: Russell King <[email protected]>
> Cc: Catalin Marinas <[email protected]>
> Cc: Will Deacon <[email protected]>
> Cc: Guo Ren <[email protected]>
> Cc: Brian Cain <[email protected]>
> Cc: Huacai Chen <[email protected]>
> Cc: WANG Xuerui <[email protected]>
> Cc: Thomas Bogendoerfer <[email protected]>
> Cc: Dinh Nguyen <[email protected]>
> Cc: Michael Ellerman <[email protected]>
> Cc: Nicholas Piggin <[email protected]>
> Cc: Christophe Leroy <[email protected]>
> Cc: Paul Walmsley <[email protected]>
> Cc: Palmer Dabbelt <[email protected]>
> Cc: Albert Ou <[email protected]>
> Cc: Yoshinori Sato <[email protected]>
> Cc: Rich Felker <[email protected]>
> Cc: John Paul Adrian Glaubitz <[email protected]>
> Cc: "David S. Miller" <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Cc: [email protected]
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: Chris Zankel <[email protected]>
> Cc: Max Filippov <[email protected]>
> Cc: Helge Deller <[email protected]>
> Cc: Arnd Bergmann <[email protected]>
> Cc: Kees Cook <[email protected]>
> Cc: "Paul E. McKenney" <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Frederic Weisbecker <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Ard Biesheuvel <[email protected]>
> Cc: Sami Tolvanen <[email protected]>
> Cc: Juerg Haefliger <[email protected]>
> Cc: Geert Uytterhoeven <[email protected]>
> Cc: Anshuman Khandual <[email protected]>
> Cc: Niklas Schnelle <[email protected]>
> Cc: "Russell King (Oracle)" <[email protected]>
> Cc: Linus Walleij <[email protected]>
> Cc: Sebastian Reichel <[email protected]>
> Cc: "Mike Rapoport (IBM)" <[email protected]>
> Cc: "Kirill A. Shutemov" <[email protected]>
> Cc: Zi Yan <[email protected]>
> Acked-by: WANG Xuerui <[email protected]> # loongarch
> ---
>   arch/Kconfig                      |  6 ++++++
>   arch/alpha/Kconfig                |  1 +
>   arch/arm/Kconfig                  |  1 +
>   arch/arm64/Kconfig                |  1 +
>   arch/csky/Kconfig                 |  1 +
>   arch/hexagon/Kconfig              |  1 +
>   arch/ia64/Kconfig                 |  1 +
>   arch/loongarch/Kconfig            |  1 +
>   arch/mips/Kconfig                 |  1 +
>   arch/nios2/Kconfig                |  1 +
>   arch/powerpc/Kconfig              |  1 +
>   arch/riscv/Kconfig                |  1 +
>   arch/sh/Kconfig                   |  1 +
>   arch/sparc/Kconfig                |  1 +
>   arch/x86/Kconfig                  |  1 +
>   arch/xtensa/Kconfig               |  1 +
>   drivers/video/Kconfig             |  3 +++
>   include/asm-generic/Kbuild        |  1 +
>   include/asm-generic/screen_info.h | 12 ++++++++++++
>   include/linux/screen_info.h       |  2 +-
>   20 files changed, 38 insertions(+), 1 deletion(-)
>   create mode 100644 include/asm-generic/screen_info.h
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 205fd23e0cada..2f58293fd7bcb 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -1466,6 +1466,12 @@ config ARCH_HAS_NONLEAF_PMD_YOUNG
>   	  address translations. Page table walkers that clear the accessed bit
>   	  may use this capability to reduce their search space.
>   
> +config ARCH_HAS_SCREEN_INFO
> +	bool
> +	help
> +	  Selected by architectures that provide a global instance of
> +	  screen_info.
> +
>   source "kernel/gcov/Kconfig"
>   
>   source "scripts/gcc-plugins/Kconfig"
> diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
> index a5c2b1aa46b02..d749011d88b14 100644
> --- a/arch/alpha/Kconfig
> +++ b/arch/alpha/Kconfig
> @@ -4,6 +4,7 @@ config ALPHA
>   	default y
>   	select ARCH_32BIT_USTAT_F_TINODE
>   	select ARCH_HAS_CURRENT_STACK_POINTER
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_MIGHT_HAVE_PC_PARPORT
>   	select ARCH_MIGHT_HAVE_PC_SERIO
>   	select ARCH_NO_PREEMPT
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 0fb4b218f6658..a9d01ee67a90e 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -15,6 +15,7 @@ config ARM
>   	select ARCH_HAS_MEMBARRIER_SYNC_CORE
>   	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>   	select ARCH_HAS_PTE_SPECIAL if ARM_LPAE
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_HAS_SETUP_DMA_OPS
>   	select ARCH_HAS_SET_MEMORY
>   	select ARCH_STACKWALK
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 343e1e1cae10a..21addc4715bb3 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -36,6 +36,7 @@ config ARM64
>   	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>   	select ARCH_HAS_PTE_DEVMAP
>   	select ARCH_HAS_PTE_SPECIAL
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_HAS_SETUP_DMA_OPS
>   	select ARCH_HAS_SET_DIRECT_MAP
>   	select ARCH_HAS_SET_MEMORY
> diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
> index 4df1f8c9d170b..28444e581fc1f 100644
> --- a/arch/csky/Kconfig
> +++ b/arch/csky/Kconfig
> @@ -10,6 +10,7 @@ config CSKY
>   	select ARCH_USE_QUEUED_RWLOCKS
>   	select ARCH_USE_QUEUED_SPINLOCKS
>   	select ARCH_HAS_CURRENT_STACK_POINTER
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_INLINE_READ_LOCK if !PREEMPTION
>   	select ARCH_INLINE_READ_LOCK_BH if !PREEMPTION
>   	select ARCH_INLINE_READ_LOCK_IRQ if !PREEMPTION
> diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig
> index 54eadf2651786..cc683c0a43d34 100644
> --- a/arch/hexagon/Kconfig
> +++ b/arch/hexagon/Kconfig
> @@ -5,6 +5,7 @@ comment "Linux Kernel Configuration for Hexagon"
>   config HEXAGON
>   	def_bool y
>   	select ARCH_32BIT_OFF_T
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
>   	select ARCH_NO_PREEMPT
>   	select DMA_GLOBAL_POOL
> diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
> index e79f15e32a451..8b1e785e6d53d 100644
> --- a/arch/ia64/Kconfig
> +++ b/arch/ia64/Kconfig
> @@ -10,6 +10,7 @@ config IA64
>   	bool
>   	select ARCH_BINFMT_ELF_EXTRA_PHDRS
>   	select ARCH_HAS_DMA_MARK_CLEAN
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_HAS_STRNCPY_FROM_USER
>   	select ARCH_HAS_STRNLEN_USER
>   	select ARCH_MIGHT_HAVE_PC_PARPORT
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index d38b066fc931b..6aab2fb7753da 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -13,6 +13,7 @@ config LOONGARCH
>   	select ARCH_HAS_FORTIFY_SOURCE
>   	select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
>   	select ARCH_HAS_PTE_SPECIAL
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>   	select ARCH_INLINE_READ_LOCK if !PREEMPTION
>   	select ARCH_INLINE_READ_LOCK_BH if !PREEMPTION
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 675a8660cb85a..c0ae09789cb6d 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -10,6 +10,7 @@ config MIPS
>   	select ARCH_HAS_KCOV
>   	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE if !EVA
>   	select ARCH_HAS_PTE_SPECIAL if !(32BIT && CPU_HAS_RIXI)
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_HAS_STRNCPY_FROM_USER
>   	select ARCH_HAS_STRNLEN_USER
>   	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
> diff --git a/arch/nios2/Kconfig b/arch/nios2/Kconfig
> index e5936417d3cd3..7183eea282212 100644
> --- a/arch/nios2/Kconfig
> +++ b/arch/nios2/Kconfig
> @@ -3,6 +3,7 @@ config NIOS2
>   	def_bool y
>   	select ARCH_32BIT_OFF_T
>   	select ARCH_HAS_DMA_PREP_COHERENT
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_HAS_SYNC_DMA_FOR_CPU
>   	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
>   	select ARCH_HAS_DMA_SET_UNCACHED
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index bff5820b7cda1..b1acad3076180 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -148,6 +148,7 @@ config PPC
>   	select ARCH_HAS_PTE_DEVMAP		if PPC_BOOK3S_64
>   	select ARCH_HAS_PTE_SPECIAL
>   	select ARCH_HAS_SCALED_CPUTIME		if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_HAS_SET_MEMORY
>   	select ARCH_HAS_STRICT_KERNEL_RWX	if (PPC_BOOK3S || PPC_8xx || 40x) && !HIBERNATION
>   	select ARCH_HAS_STRICT_KERNEL_RWX	if PPC_85xx && !HIBERNATION && !RANDOMIZE_BASE
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 5966ad97c30c3..b5a48f8424af9 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -29,6 +29,7 @@ config RISCV
>   	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>   	select ARCH_HAS_PMEM_API
>   	select ARCH_HAS_PTE_SPECIAL
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_HAS_SET_DIRECT_MAP if MMU
>   	select ARCH_HAS_SET_MEMORY if MMU
>   	select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
> diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
> index 04b9550cf0070..001f5149952b4 100644
> --- a/arch/sh/Kconfig
> +++ b/arch/sh/Kconfig
> @@ -10,6 +10,7 @@ config SUPERH
>   	select ARCH_HAS_GIGANTIC_PAGE
>   	select ARCH_HAS_GCOV_PROFILE_ALL
>   	select ARCH_HAS_PTE_SPECIAL
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>   	select ARCH_HIBERNATION_POSSIBLE if MMU
>   	select ARCH_MIGHT_HAVE_PC_PARPORT
> diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
> index 8535e19062f65..e4bfb80b48cfe 100644
> --- a/arch/sparc/Kconfig
> +++ b/arch/sparc/Kconfig
> @@ -13,6 +13,7 @@ config 64BIT
>   config SPARC
>   	bool
>   	default y
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_MIGHT_HAVE_PC_PARPORT if SPARC64 && PCI
>   	select ARCH_MIGHT_HAVE_PC_SERIO
>   	select DMA_OPS
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 53bab123a8ee4..d7c2bf4ee403d 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -91,6 +91,7 @@ config X86
>   	select ARCH_HAS_NONLEAF_PMD_YOUNG	if PGTABLE_LEVELS > 2
>   	select ARCH_HAS_UACCESS_FLUSHCACHE	if X86_64
>   	select ARCH_HAS_COPY_MC			if X86_64
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_HAS_SET_MEMORY
>   	select ARCH_HAS_SET_DIRECT_MAP
>   	select ARCH_HAS_STRICT_KERNEL_RWX
> diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
> index 3c6e5471f025b..c6cbd7459939c 100644
> --- a/arch/xtensa/Kconfig
> +++ b/arch/xtensa/Kconfig
> @@ -8,6 +8,7 @@ config XTENSA
>   	select ARCH_HAS_DMA_PREP_COHERENT if MMU
>   	select ARCH_HAS_GCOV_PROFILE_ALL
>   	select ARCH_HAS_KCOV
> +	select ARCH_HAS_SCREEN_INFO
>   	select ARCH_HAS_SYNC_DMA_FOR_CPU if MMU
>   	select ARCH_HAS_SYNC_DMA_FOR_DEVICE if MMU
>   	select ARCH_HAS_DMA_SET_UNCACHED if MMU
> diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
> index 8b2b9ac37c3df..d4a72bea56be0 100644
> --- a/drivers/video/Kconfig
> +++ b/drivers/video/Kconfig
> @@ -21,6 +21,9 @@ config STI_CORE
>   config VIDEO_CMDLINE
>   	bool
>   
> +config ARCH_HAS_SCREEN_INFO
> +	bool
> +
>   config VIDEO_NOMODESET
>   	bool
>   	default n
> diff --git a/include/asm-generic/Kbuild b/include/asm-generic/Kbuild
> index 941be574bbe00..5e5d4158a4b4b 100644
> --- a/include/asm-generic/Kbuild
> +++ b/include/asm-generic/Kbuild
> @@ -47,6 +47,7 @@ mandatory-y += percpu.h
>   mandatory-y += pgalloc.h
>   mandatory-y += preempt.h
>   mandatory-y += rwonce.h
> +mandatory-y += screen_info.h
>   mandatory-y += sections.h
>   mandatory-y += serial.h
>   mandatory-y += shmparam.h
> diff --git a/include/asm-generic/screen_info.h b/include/asm-generic/screen_info.h
> new file mode 100644
> index 0000000000000..6fd0e50fabfcd
> --- /dev/null
> +++ b/include/asm-generic/screen_info.h
> @@ -0,0 +1,12 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef _ASM_GENERIC_SCREEN_INFO_H
> +#define _ASM_GENERIC_SCREEN_INFO_H
> +
> +#include <uapi/linux/screen_info.h>
> +
> +#if defined(CONFIG_ARCH_HAS_SCREEN_INFO)
> +extern struct screen_info screen_info;
> +#endif
> +
> +#endif /* _ASM_GENERIC_SCREEN_INFO_H */
> diff --git a/include/linux/screen_info.h b/include/linux/screen_info.h
> index eab7081392d50..c764b9a51c24b 100644
> --- a/include/linux/screen_info.h
> +++ b/include/linux/screen_info.h
> @@ -4,6 +4,6 @@
>   
>   #include <uapi/linux/screen_info.h>
>   
> -extern struct screen_info screen_info;
> +#include <asm/screen_info.h>
>   
>   #endif /* _SCREEN_INFO_H */