On Thu, Dec 15, 2011 at 02:50:47PM -0600, Timur Tabi wrote:

I'm cleaning up my fbdev driver, and I just noticed FBINFO_VIRTFB:

#define FBINFO_VIRTFB		0x0004 /* FB is System RAM, not device. */

I am currently not setting this flag, but I am allocating my framebuffer in system ram via dma_alloc_coherent().  I don't see any good documentation for this flag, but I suspect I should be enabling it.  What exactly does this flag do?

It basically inhibits from using VM_IO which should not be set on
System RAM. In your case you are using System RAM, so please do set it.

I'd also like some explanation for these two macros, which appear to be related:

#define FBINFO_PARTIAL_PAN_OK	0x0040 /* otw use pan only for double-buffering */
#define FBINFO_READS_FAST	0x0080 /* soft-copy faster than rendering */

Not really. They have a different function, but you are better of looking in the code
to see how they are used.

-- 
Timur Tabi
Linux kernel developer at Freescale

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