Hi All,
I am not sure if this is the right place to ask these questions. I am
new to this list. Does this list offer any help to device driver
developers? I appreciate if any one could give an answer to these
questions.
1. In 2.6 kernel, even if I set the sg_tablesize to SG_NONE, the
mid-layer is still queuing commands with use_sg=1. There is no way to
disable this SG at all? I do not need a sg_table as I do not use any DMA
or anything else. With SG_NONE, the use_sg is always set to 1 and the IO
size queued by mid layer is only 512 bytes and decreases the throughput
very badly.
2. One of the challenge I am facing is that the scatterlist structure is
changed. There is no virtual address, but they replaced this with a page
and offset fields. Since I need only the virtual addresses for the
actual buffer (No DMA), I am using the following method to calculate the
virtual address.
address=page_address(sg[i].page) + sg[i].offset;
Is this the right way? I am assuming that sg[i].page will be mapped in
to kernel address space as this address is created by SCSI mid-layer. Is
that right? Or do I have to use kmap? I tried replacing page_address
with kmap/kunmap. But as soon as call kunmap to unmap, the kernal
panics! Any thoughts?
3. Do I have to disable bottom halves before calling scsi_done()? It
seems that the kernel panics when I call scsi_done if I use spin_lock
instead of spin_lock_bh(). This is one of my spin_locks created for
protecting a data structure.
Thanks in advance,
Aboo
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