Hi Geert,
Am 04.05.2018 um 19:24 schrieb Geert Uytterhoeven:
Hi Michael,
Yes, that would be useful. The other assumption could be that
platform devices always allow an all-0xff dma mask.
That's not always true (Atari NCR5380 SCSI and floppy would use a 24
bit DMA mask). We use bounce buffers allocated from a dedicated lowmem
pool there currently, and for all I know don't use the DMA API yet.
I bet that is a rare exception though. Setting the default DMA mask
for platform devices to all-0xff and letting the few odd drivers force
a different setting seems the best way forward.
I'd say that's usually a property of the platform, not of the device?
Right - I was thinking 'm68k' as platform, not a particular machine like
Mac or Falcon (the 24 bit mask only applies to that particular model
anyway).
So IMHO it belongs in the platform code, not in the device driver code.
OK - let's have a default mask of 64 bit, and allow machine specific
platform_init() to override using a new helper function.
Cheers,
Michael
Gr{oetje,eeting}s,
Geert
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