x86: allow CONFIG_ISA_DMA_API to be disabled (1c00f016) · Commits · 戴 / test

Not all 64-bit systems require ISA-style DMA, so allow it to be configurable. x86 utilizes the generic ISA DMA allocator from kernel/dma.c, so require it only when CONFIG_ISA_DMA_API is enabled. Disabling CONFIG_ISA_DMA_API is dependent on x86_64 since those machines do not have ISA slots and benefit the most from disabling the option (and on CONFIG_EXPERT as required by H. Peter Anvin). When disabled, this also avoids declaring claim_dma_lock(), release_dma_lock(), request_dma(), and free_dma() since those interfaces will no longer be provided. Signed-off-by:

David Rientjes <rientjes@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Bjorn Helgaas <bjorn.helgaas@hp.com> Cc: Russell King <linux@arm.linux.org.uk> Cc: "Luck, Tony" <tony.luck@intel.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/Kconfig

+7 −3

Original line number	Diff line number	Diff line
		@@ -123,7 +123,7 @@ config NEED_SG_DMA_LENGTH
		def_bool y

		config GENERIC_ISA_DMA
		def_bool y
		def_bool ISA_DMA_API

		config GENERIC_IOMAP
		def_bool y
		@@ -2002,9 +2002,13 @@ source "drivers/pci/pcie/Kconfig"

		source "drivers/pci/Kconfig"

		# x86_64 have no ISA slots, but do have ISA-style DMA.
		# x86_64 have no ISA slots, but can have ISA-style DMA.
		config ISA_DMA_API
		def_bool y
		bool "ISA-style DMA support" if (X86_64 && EXPERT)
		default y
		help
		Enables ISA-style DMA support for devices requiring such controllers.
		If unsure, say Y.

		if X86_32

arch/x86/include/asm/dma.h

+5 −1

Original line number	Diff line number	Diff line
		@@ -151,6 +151,7 @@
		#define DMA_AUTOINIT 0x10


		#ifdef CONFIG_ISA_DMA_API
		extern spinlock_t dma_spin_lock;

		static inline unsigned long claim_dma_lock(void)
		@@ -164,6 +165,7 @@ static inline void release_dma_lock(unsigned long flags)
		{
		spin_unlock_irqrestore(&dma_spin_lock, flags);
		}
		#endif /* CONFIG_ISA_DMA_API */

		/* enable/disable a specific DMA channel */
		static inline void enable_dma(unsigned int dmanr)
		@@ -303,9 +305,11 @@ static inline int get_dma_residue(unsigned int dmanr)
		}


		/* These are in kernel/dma.c: */
		/* These are in kernel/dma.c because x86 uses CONFIG_GENERIC_ISA_DMA */
		#ifdef CONFIG_ISA_DMA_API
		extern int request_dma(unsigned int dmanr, const char *device_id);
		extern void free_dma(unsigned int dmanr);
		#endif

		/* From PCI */

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