Re: kernel BUG while reading from SPI into static buffer
On 13 May 2011 20:02, Mulyadi Santosa mulyadi.sant...@gmail.com wrote: Feel free to try to observer whether this statement is correct or not... and you should check the address of buffer when declared as static I guess I did, and here's the result: Local Buffer - 0xc3a61edd Static Buffer - 0xbf03eac1 So they indeed seem to be way apart in memory :). On 13 May 2011 20:38, Greg KH g...@kroah.com wrote: Don't statically allocate memory for spi, you need to dynamically allocate it with 'kmalloc'. The fact that the first time didn't crash for you was just lucky. I'm guessing you say this because static variables are not in DMA capable memory. But how exactly do we figure out which part of memory is DMA-capable and which isn't? Also, is this a restriction imposed by the kernel or by the hardware? Thanks Regards, Felix. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: kernel BUG while reading from SPI into static buffer
Need to add... On Fri, May 13, 2011 at 21:32, Mulyadi Santosa mulyadi.sant...@gmail.com wrote: OK, a bit clear now so, I can say base on the above code snippet, buffer...when declared as static, somehow falls into non ZONE_NORMAL..i.e non directly mapped memory area... what I precisely mean, it falls into non DMA able zone... -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: kernel BUG while reading from SPI into static buffer
On Fri, May 13, 2011 at 12:33:15PM +0530, Felix Varghese wrote: Hi, I am trying to read some data via SPI on an a modified (custom SPI device attached) AT91SAM9G20-EK board. If I pass a local array buffer, declared as char buffer[100]; as the rx_buf pointer for the spi transfer, the code works fine. But if I just change the declaration to static char buffer[100] instead, I get the following crash: Don't statically allocate memory for spi, you need to dynamically allocate it with 'kmalloc'. The fact that the first time didn't crash for you was just lucky. hope this helps, greg k-h ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
