Messages in this thread | | | Date | Thu, 9 Dec 2010 13:09:36 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH 1/2] memstick: add support for legacy memorysticks |
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On Thu, 9 Dec 2010 04:42:25 +0200 Maxim Levitsky <maximlevitsky@gmail.com> wrote:
> +/* > + * Advance scatterlist by 'consumed' bytes > + * Returns new scatterlist, or NULL if can't advance that much > + */ > +static struct scatterlist *sg_advance(struct scatterlist *sg, int consumed) > +{ > + while (consumed >= sg->length) { > + consumed -= sg->length; > + > + sg = sg_next(sg); > + if (!sg) > + break; > + } > + > + WARN_ON(!sg && consumed); > + > + if (!sg) > + return NULL; > + > + sg->offset += consumed; > + sg->length -= consumed; > + > + if (sg->offset >= PAGE_SIZE) { > + struct page *page = > + nth_page(sg_page(sg), sg->offset / PAGE_SIZE); > + sg_set_page(sg, page, sg->length, sg->offset % PAGE_SIZE); > + } > + > + return sg; > +} > + > +/* Calculate number of sg entries in sg list */ > +static int sg_nents(struct scatterlist *sg) > +{ > + int nents = 0; > + while (sg) { > + nents++; > + sg = sg_next(sg); > + } > + > + return nents; > +} > + > +/* Calculate total lenght of scatterlist */
(typo)
> +static int sg_total_len(struct scatterlist *sg) > +{ > + int len = 0; > + while (sg) { > + len += sg->length; > + sg = sg_next(sg); > + } > + return len; > +} > + > +/* Compare contents of an sg to a buffer */ > +static bool sg_compare_to_buffer(struct scatterlist *sg, u8 *buffer, size_t len) > +{ > + unsigned long flags; > + int retval = 0; > + struct sg_mapping_iter miter; > + > + if (sg_total_len(sg) < len) > + return 1; > + > + local_irq_save(flags); > + sg_miter_start(&miter, sg, sg_nents(sg), > + SG_MITER_ATOMIC | SG_MITER_FROM_SG); > + > + while (sg_miter_next(&miter) && len > 0) { > + > + int cmplen = min(miter.length, len); > + if (memcmp(miter.addr, buffer, cmplen)) { > + retval = 1; > + break; > + } > + > + buffer += cmplen; > + len -= cmplen; > + } > + > + sg_miter_stop(&miter); > + local_irq_restore(flags); > + return retval; > +}
I think I mentioned this before, but ... it's really bad that the above functions appear in a particular device driver. They are, to varying degrees, independent of that driver and should be provided by the sglist core code.
Also, the local_irq_save/restore in sg_compare_to_buffer() is quite mysterious and should have a comment explaining why it is there. Once that's done, I might understand why it isn't a bug on SMP machines ;)
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