On Fri, Apr 28, 2023, at 13:27, Geert Uytterhoeven wrote:
On Fri, Apr 28, 2023 at 2:18 PM Robin Murphy <robin.murphy@xxxxxxx> wrote:
On 2023-04-28 10:27, Thomas Zimmermann wrote:
-
-#elif defined(__i386__) || defined(__alpha__) || defined(__x86_64__) || \
- defined(__hppa__) || defined(__sh__) || defined(__powerpc__) || \
- defined(__arm__) || defined(__aarch64__) || defined(__mips__)
-
-#define fb_readb __raw_readb
-#define fb_readw __raw_readw
-#define fb_readl __raw_readl
-#define fb_readq __raw_readq
-#define fb_writeb __raw_writeb
-#define fb_writew __raw_writew
-#define fb_writel __raw_writel
-#define fb_writeq __raw_writeq
Note that on at least some architectures, the __raw variants are
native-endian, whereas the regular accessors are explicitly
little-endian, so there is a slight risk of inadvertently changing
behaviour on big-endian systems (MIPS most likely, but a few old ARM
platforms run BE as well).
Also on m68k, when ISA or PCI are enabled.
In addition, the non-raw variants may do some extras to guarantee
ordering, which you do not need on a frame buffer.
So I'd go for the __raw_*() variants everywhere.
The only implementations in fbdev are
1) sparc sbus
2) __raw_writel
3) direct pointer dereference
But none use the byte-swapping writel() implementations, and
the only ones that use the direct pointer dereference or sbus
are the ones on which these are defined the same as __raw_writel
Arnd
