> --- a/include/linux/dma-attrs.h
> +++ b/include/linux/dma-attrs.h
> @@ -0,0 +1,33 @@
> +#ifndef _DMA_ATTR_H
> +#define _DMA_ATTR_H
> +
> +#include <linux/bug.h>
> +
> +enum {
> + DMA_ATTR_INVALID,
> + DMA_ATTR_BARRIER,
> + DMA_ATTR_FOO,
> + DMA_ATTR_GOO,
> + DMA_ATTR_MAX,
> +};
> +
> +struct dma_attrs {
> + unsigned flags;
> +};
> +
> +static inline int dma_set_attr(struct dma_attrs *attrs, unsigned attr) {
maybe this would be cleaner if you named the DMA_ATTR enum and used
that instead of unsigned here (and below)?
> + BUG_ON(attrs == NULL);
does this BUG_ON() buy us much? It seems the only thing we would fail
to oops on is if someone did dma_set_attr(NULL, INVALID) and I'm not
sure it's worth it to BUG here.
> + if (attr > DMA_ATTR_INVALID && attr < DMA_ATTR_MAX) {
> + attrs->flags = (1 << attr);
> + return 0;
> + }
> + return 1;
returning -EINVAL here instead of 1 would probably be more "kernelish".
> +}
> +
> +static inline int dma_get_attr(struct dma_attrs *attrs, unsigned attr) {
> + if (attrs)
> + return attrs->flags & (1 << attr);
so it's OK to pass attrs == NULL into dma_get_attr() but not into
dma_set_attr()? seems kind of odd.
> + return 0;
> +}
It seems you're missing a way to initialize a struct dma_attrs. How
do I clear the flags field to start with?
A macro like DEFINE_DMA_ATTRS() that initializes things for you (like
LIST_HEAD or DEFINE_SPIN_LOCK) would probably be a good thing to have
as well.
Also I guess you could test ARCH_USES_DMA_ATTRS in this file and stub
everything out and define an empty structure if it's not defined.
save a few bytes of stack etc.
> +
> +#endif /* _DMA_ATTR_H */
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