[PATCH] ACPI CMOS region support rev. 4

[Ian Smith]

On Mon, 16 Mar 2015 11:50:59 -0400, Anthony Jenkins wrote:
 > On 03/16/2015 11:00 AM, Anthony Jenkins wrote:
 > > On 03/16/2015 09:59 AM, Ian Smith wrote:
 > >> On Sat, 14 Mar 2015 23:40:34 -0400, Anthony Jenkins wrote:
 > >>> +    if (!acpi_check_rtc_byteaccess(function == ACPI_READ, address))
 > >>> +            return AE_BAD_PARAMETER;
 > >> acpi_check_rtc_byteaccess() needs to be called per byte of 1, 2 or 4 
 > >> bytes - or pass it 'bytes' also, and loop over each of them within?
 > >> =======
 > >>
 > >> Otherwise (for example) a 2 byte read from 0x0b or 4 byte read from 
 > >> 0x09-0x0b will read 0x0c (clearing interrupts), or a 2 or 4 byte write 
 > >> to (say) 0x01 will also write to 0x02 and 0x04 (clobbering the time).
 > > Right, this is an (incorrect) hybrid of a few attempts, probably from
 > > around the time I lost my SSD and only had a single backup copy of my
 > > work to go from.  In one revision I had disallowed all multibyte
 > > accesses (width > 8) since IMHO it was more consistent/correct with the
 > > suggested locking.  I wasn't ignoring your suggestion, just making one
 > > or a few changes at a time (generally the simpler ones).
 > 
 > Okay now I remember why I was reluctant to do this - suppose ACPIBIOS
 > does a multibyte op on a set of bytes whose last byte fails
 > acpi_check_rtc_byteaccess().  I will have already performed n-1
 > accesses.  At one point I had a revision (acpi_check_rtc_access()?) that
 > permitted/denied the entire request (it took the starting address and
 > byte length), but I guess that got lost too.  I'll just recreate it...

Yep, validating all access before doing any sounds like the way to go.

Also, bytes = width >> 3 is ok, since you then affirm !(width & 0x07), 
so non-multiples of 8 bits are invalidated anyway.  You should still 
check that width (or bytes) > 0, even if 0 should never be passed.

I guess the Big Kids will start playing once this hits bugzilla? :)

cheers, Ian