Messages in this thread |  | | Date | Sat, 1 Oct 2016 11:25:05 +0200 | From | Boris Brezillon <> | Subject | Re: [PATCH] mtd: mtk: avoid warning in mtk_ecc_encode |
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On Fri, 30 Sep 2016 19:25:17 +0200 Arnd Bergmann <arnd@arndb.de> wrote:
> 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).
I agree, even though calling something prefixed with __ (in this case, __ioread32_copy()) sounds like a bad thing too :).
> > - the min(len,4) expression is incorrect, fixing that makes it more complicated > again
Sorry, it's min(len - i, 4), which is not that complicated :P.
> > - 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).
Okay.
> > I agree that he 112 byte buffer isn't ideal either, it just seemed to > be the lesser annoyance.
How about we keep your approach, but put the buffer in the mtk_ecc struct?
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