Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH] mtd: mtk: avoid warning in mtk_ecc_encode | Date | Fri, 30 Sep 2016 19:25:17 +0200 |
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On Friday 30 September 2016, Boris Brezillon wrote: > > + /* copy into possibly unaligned OOB region with actual length */ > > + memcpy(data + bytes, eccdata, len); > > Is it better than > > for (i = 0; i < len; i += 4) { > u32 val = __raw_readl(ecc->regs + ECC_ENCPAR(i / 4)); > > memcpy(data + bytes + i, &val, min(len, 4)); > } > > I'm probably missing something, but what's the point of creating a > temporary buffer of 112 bytes on the stack since you'll have to copy > this data to the oob buffer at some point?
I tried something like that first, but wasn't too happy with it for a number of small reasons:
- __raw_readl in a driver is not usually the right API, __memcpy32_from_io uses it internally, but it's better for a driver not to rely on that, in case we need some barriers (which we may in factt need for other drivers).
- the min(len,4) expression is incorrect, fixing that makes it more complicated again
- I didn't like to call memcpy() multiple times, as that might get turned into an external function call (the compiler is free to optimize small memcpy calls or not).
I agree that he 112 byte buffer isn't ideal either, it just seemed to be the lesser annoyance.
Arnd
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