Re: [PATCH] Tile Blitting

On Sun, 2003-03-02 at 20:14, Geert Uytterhoeven wrote:

On Thu, 27 Feb 2003, James Simmons wrote:

quoted

quoted

On Don, 2003-02-27 at 15:15, Antonino Daplas wrote: 

quoted

On Thu, 2003-02-27 at 09:18, James Simmons wrote:
 

quoted

quoted

Thus, the restriction that the buffer must be completely copied by the
driver before returning.  And because of this restriction, an extra copy
which might be unnecessary cannot be avoided (this was noted by Petr).

Treating the buffer as a ringbuffer, we eliminate these restrictions.

I didn't realize that the below was a ringbuffer implementation. The name
threw me off. 

Well, it's not strictly a ringbuffer implementation.  This would require
a head and tail pointer where fbcon will adjust the tail and the
driver/hardware will adjust the head.  This will be very difficult to
implement in a device independent manner.  So we just cheat by issuing
an fb_sync() per loop to flush all pending commands.

That still seems suboptimal though. What the DRM often does is have the
chip write an age value to a scratch register when it's done processing
something. Maybe something like that could be used to avoid waiting for
the chip to go idle at all?

Don't waste your time. I'm removing all the changes that have been done 
since 2.5.51. After that I will no longer be co-maintainter of the 
framebuffer layer. 

Are you sure about that?!?!?

I agree.  Actually, I'm not worried about Tile blitting.  It should be
mature since it's basically a rehash of the 2.4 API.  If I'm going to
worry about something, it's the standard accel_putcs() code, especially
if thread-safety is an issue.

Is thread-safety a real problem?  That was also my concern before, which
is why I looked at vt.c.  From what I can see, there's always an
"acquire_console_sem()" before calling any of the console methods. The
console semaphore is supposed to guarantee serialization and exclusive
access to the console (see linux/kernel/printk.c).

Tony



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