Greetings,
On 12-Sep-01 Oliver Neukum wrote:
>> The second bug report said the module works fine when the person limits
>> his
>> memory to 960 MB (how, I dont know). With full memory, he gets artefacts
>
> With a 'mem=' kernel command line I presume.
>
>> which to me suggests the second frame buffer is allocated, but somehow in
>> memory which isnt accessible (every other frame is bright pink --> filled
>> with 0xFF before YUV->RGB translation?)
>
> Not accessible by whom ?
> The USB controller or the CPU ? 1GB should be accessible to the USB
> controller.
The CPU; there are 3 buffers involved; a DMA-able buffer used for the ISO
transfers (kmalloc()ed), a ring buffer for whole frames (vmalloc()ed), and
finally the image buffer that is used for decompression (rvmalloc()ed, and
mmap()able). The frame buffers seem to have trouble during vmalloc.
I�m wondering... I�m vmallocing 3 buffers in rapid succession during open();
is there possibly a limit to the number of vmalloc()ed areas a process may
have?
Also I noticed my driver is the only USB driver allocating memory with
vmalloc(); others use rvmalloc() or vmalloc_32() directly.
>> Unfortunately Im not rich enough to put 1GB of RAM in my machine to test
>> this... ;-(
>
> If it is indeed a problem of accessability by the CPU you might use the
> patch
> Andrea Arcangeli has written which allows you the use highmen with 128MB.
You mean his patch simulates the highmem stuff on machines with less than 1
GB? That might be worth a try (mine has 320 MB RAM; plenty to play around
with). But no, it doesn�t seem like a CPU problem (the data is copied from
the ISO buffers to the frame buffers with a simple memcpy()).
- Nemosoft
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