On 7/29/23 15:21, Thomas Zimmermann wrote:
Hi Helge
Am 29.07.23 um 08:51 schrieb Helge Deller:
On 7/28/23 23:01, Sam Ravnborg wrote:
Hi Helge,
On Fri, Jul 28, 2023 at 08:46:59PM +0200, Helge Deller wrote:
On 7/28/23 18:39, Thomas Zimmermann wrote:
Most fbdev drivers operate on I/O memory.
Just nitpicking here:
What is I/O memory?
Isn't it either memory, or I/O ?
I mean, I would never think of the cfb* draw functions under I/O.
And most of those use the
default implementations for file I/O and console drawing. Convert all
these low-hanging fruits to the fb_ops initializer macro and Kconfig
token for fbdev I/O helpers.
I do see the motivation for your patch, but I think the
macro names are very misleading.
You have:
#define __FB_DEFAULT_IO_OPS_RDWR \
.fb_read = fb_io_read, \
.fb_write = fb_io_write
#define __FB_DEFAULT_IO_OPS_DRAW \
.fb_fillrect = cfb_fillrect, \
.fb_copyarea = cfb_copyarea, \
.fb_imageblit = cfb_imageblit
#define __FB_DEFAULT_IO_OPS_MMAP \
.fb_mmap = NULL /* default implementation */
#define FB_DEFAULT_IO_OPS \
__FB_DEFAULT_IO_OPS_RDWR, \
__FB_DEFAULT_IO_OPS_DRAW, \
__FB_DEFAULT_IO_OPS_MMAP
I think FB_DEFAULT_IO_OPS is OK for read/write/mmap.
But I would suggest to split out __FB_DEFAULT_IO_OPS_DRAW.
Something like:
#define FB_DEFAULT_IO_OPS \
__FB_DEFAULT_IO_OPS_RDWR, \
__FB_DEFAULT_IO_OPS_MMAP
#define FB_DEFAULT_CFB_OPS \
.fb_fillrect = cfb_fillrect, \
.fb_copyarea = cfb_copyarea, \
.fb_imageblit = cfb_imageblit
The prefix cfb, I have recently learned, equals color frame buffer.
correct.
They are named such for purely historical reasons.
well, they operate on MEMORY which represents a (color) frame buffer,
either in host memory or memory on some card on some bus.
So, the naming cfb is not historical, but even today correct.
What is important is where the data are copied as we have two
implementations of for example copyarea - one using system memory, the
other using IO memory.
sys_copyarea() and cfb_copyarea().
The naming FB_DEFAULT_IO_OPS says this is the defaults to IO memory
operations, which tell what they do
This is exactly what I find misleading. IO_OPS sounds that it operates
on file I/O (like file read/write), but not on iomem.
and avoid the strange cfb acronym.
Reserve cfb for color frame buffers only - and maybe in the end rename
the three cfbcopyarea, cfbfillrect, cfbimgblt to use the io prefix.
Again, the io prefix is what I think is misleading.
Why not name it what it really is and what is used in the kernel already, e.g.
iomem_copyarea() and sysmem_copyarea().
which would lead to
FB_DEFAULT_IOMEM_OPS and FB_DEFAULT_SYSMEM_OPS.
Yes there's been a bit of confusion and discussion on the naming before. I'd be happy if we can standardize on sysmem and iomem.
I can add a patch to this patchset to rename the _IO_ macros and tokens to use _IOMEM_. That's not too much change. A later patchset can address sysmem and deferred I/O helpers separately.
Sound good.
On motivation: for now it's a cleanup to make the a bit code easier to understand. But once all drivers set their callbacks correctly, we can make the I/O mem code optional. It's currently the default and built-in unconditionally. But it's not uncommon that it's unused entirely.
Probably true for x86, on others it might be useful to make the sysmem optional as well. I did not checked.
Anyway, thanks for your work!
Helge
Best regards
Thomas
Which is much simpler to do after this series - and nice extra benefit.
I hope this properly explains why I like the current naming and
acked it when the macros were introduced.
IMHO the naming isn't perfect, but that's just nitpicking.
Besides that, Thomas' patches are a nice cleanup.
So, if you want add a
Acked-by: Helge Deller <deller@xxxxxx>
to the series.
Helge
