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    SubjectRe: [PATCH/RFC 4/6] mm: Add NO_DMA dummies for DMA pool API
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    Hi Geert,

    On 06/02/18 10:14, Geert Uytterhoeven wrote:
    > Add dummies for dma{,m}_pool_{create,destroy,alloc,free}(), to allow
    > compile-testing if NO_DMA=y.
    >
    > This prevents the following from showing up later:
    >
    > ERROR: "dma_pool_destroy" [drivers/usb/mtu3/mtu3.ko] undefined!
    > ERROR: "dma_pool_free" [drivers/usb/mtu3/mtu3.ko] undefined!
    > ERROR: "dma_pool_alloc" [drivers/usb/mtu3/mtu3.ko] undefined!
    > ERROR: "dma_pool_create" [drivers/usb/mtu3/mtu3.ko] undefined!
    > ERROR: "dma_pool_destroy" [drivers/scsi/hisi_sas/hisi_sas_main.ko] undefined!
    > ERROR: "dma_pool_free" [drivers/scsi/hisi_sas/hisi_sas_main.ko] undefined!
    > ERROR: "dma_pool_alloc" [drivers/scsi/hisi_sas/hisi_sas_main.ko] undefined!
    > ERROR: "dma_pool_create" [drivers/scsi/hisi_sas/hisi_sas_main.ko] undefined!
    > ERROR: "dma_pool_alloc" [drivers/mailbox/bcm-pdc-mailbox.ko] undefined!
    > ERROR: "dma_pool_free" [drivers/mailbox/bcm-pdc-mailbox.ko] undefined!
    > ERROR: "dma_pool_create" [drivers/mailbox/bcm-pdc-mailbox.ko] undefined!
    > ERROR: "dma_pool_destroy" [drivers/mailbox/bcm-pdc-mailbox.ko] undefined!
    >
    > Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
    > ---
    > include/linux/dmapool.h | 21 +++++++++++++++++++--
    > 1 file changed, 19 insertions(+), 2 deletions(-)
    >
    > diff --git a/include/linux/dmapool.h b/include/linux/dmapool.h
    > index 53ba737505df31c7..adeb5e56c3ad73a8 100644
    > --- a/include/linux/dmapool.h
    > +++ b/include/linux/dmapool.h
    > @@ -16,6 +16,7 @@
    >
    > struct device;
    >
    > +#ifdef CONFIG_HAS_DMA
    > struct dma_pool *dma_pool_create(const char *name, struct device *dev,
    > size_t size, size_t align, size_t allocation);
    >
    > @@ -23,6 +24,17 @@ void dma_pool_destroy(struct dma_pool *pool);
    >
    > void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
    > dma_addr_t *handle);
    > +void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t addr);
    > +#else /* !CONFIG_HAS_DMA */
    > +static inline struct dma_pool *dma_pool_create(const char *name,
    > + struct device *dev, size_t size, size_t align, size_t allocation)
    > +{ return NULL; }
    > +static inline void dma_pool_destroy(struct dma_pool *pool) { }
    > +static inline void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
    > + dma_addr_t *handle) { return NULL; }
    > +static inline void dma_pool_free(struct dma_pool *pool, void *vaddr,
    > + dma_addr_t addr) { }
    > +#endif /* !CONFIG_HAS_DMA */
    >
    > static inline void *dma_pool_zalloc(struct dma_pool *pool, gfp_t mem_flags,
    > dma_addr_t *handle)
    > @@ -30,14 +42,19 @@ static inline void *dma_pool_zalloc(struct dma_pool *pool, gfp_t mem_flags,
    > return dma_pool_alloc(pool, mem_flags | __GFP_ZERO, handle);
    > }
    >
    > -void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t addr);
    > -
    > /*
    > * Managed DMA pool
    > */
    > +#ifdef CONFIG_HAS_DMA
    > struct dma_pool *dmam_pool_create(const char *name, struct device *dev,
    > size_t size, size_t align, size_t allocation);
    > void dmam_pool_destroy(struct dma_pool *pool);
    > +#else /* !CONFIG_HAS_DMA */
    > +static inline struct dma_pool *dmam_pool_create(const char *name,
    > + struct device *dev, size_t size, size_t align, size_t allocation)
    > +{ return NULL; }
    > +static inline void dmam_pool_destroy(struct dma_pool *pool) { }
    > +#endif /* !CONFIG_HAS_DMA */

    Nit: It might be tidier to add *all* the stubs down here so that there
    only need be a single #ifdef, then move the dma_pool_zalloc definition
    outside at the end (where we might eventually get rid of it anyway).

    Other than that, though, I think I agree with the series in general -
    more COMPILE_TEST is always good from the point of view of weeding out
    drivers using architecture-specific DMA API internals which aren't part
    of the proper generic interface.

    Robin.

    >
    > #endif
    >
    >

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