usb_bulk_msg timeout w/ rvmalloc

usb_bulk_msg timeout w/ rvmalloc

[paul.thacker]

     I have written a driver which, in part, facilitates the usb bulk 
     transfer of raw image data. It works fine for small (CIF, QCIF) 
     images, but for larger images, kmalloc will not allocate enough 
     memory. 
     
     I copied the rvmalloc code from the cpia2 driver and used it in place 
     of kmalloc. The memory allocates fine, but usb_bulk_msg now times out 
     when using the pointer to the rvmalloc'd memory. I have been unable to 
     find an instance of an existing driver using rvmalloc in conjunction 
     with usb_bulk_msg. 
     
     Thanks in advance for any advice. Please reply via email - I am not 
     subscribed to the mailing list.
     
     Paul Thacker
     Staff Engineer II
     ST Microelectronics
     paul.thacker@st.com

Re: usb_bulk_msg timeout w/ rvmalloc

[Pete Zaitcev]

>      I have written a driver which, in part, facilitates the usb bulk 
>      transfer of raw image data. It works fine for small (CIF, QCIF) 
>      images, but for larger images, kmalloc will not allocate enough 
>      memory. 

How much do you need?
     
>      I copied the rvmalloc code from the cpia2 driver and used it in place 
>      of kmalloc. The memory allocates fine, but usb_bulk_msg now times out 
>      when using the pointer to the rvmalloc'd memory. I have been unable to 
>      find an instance of an existing driver using rvmalloc in conjunction 
>      with usb_bulk_msg. 

The best thing would be to use pipelined transfer with
several URBs, I think. If that is too difficult for you,
try to use __get_free_pages(), but mind that even if free
RAM is available, kernel may not be able to fulfill your
request. Check response codes carefuly.

-- Pete