On Sun, Feb 20, 2011 at 3:57 PM, Colin Cross <ccross@xxxxxxxxxxx> wrote: > On Sun, Feb 20, 2011 at 3:38 PM, Ben Dooks <ben-i2c@xxxxxxxxx> wrote: > <snip> > >>> > you know, there's a readsl() function that does this. >>> I think readsl can't handle the possibly unaligned buf pointer. >> >> it does. see arch/arm/lib/io-writesl.S for proof. > You're right, I traced the wrong definition of readsl/writesl > >>> > this whole function gives me the creeps, is there any reason why >>> > we can't use the readsl or similar functions for this? >>> Same here - readsl can't handle the alignment requirements, readsb >>> can't handle the required 32 bit register read, and the bytes in the >>> same word but after the end buf may not be part of buf, so byte writes >>> to buf are required. >> >> You'll find it can, too. arch/arm/lib/io-readsl.S. > I still think readsl doesn't work here. It may need to read 7 bytes, > requiring 2 calls to readl, but 1 word write and 3 byte writes to buf. > Using readsl for the whole buffer would overwrite the 8th byte. I > can use readsl for the main loop, but I will still need to write the > last 1-3 bytes separately. I could use readl and memcpy to do the > last writes. Actually, the same problem applies to writesl. If the buffer is not aligned, reading an entire word to get the partial word at the end of the buffer may cross a page boundary and fault. I'll have to use writesl for the whole words and then handle the last partial word with memcpy and writel. -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
