On 02/06/2012 05:05 PM, Vasanthakumar Thiagarajan wrote: > On Mon, Feb 06, 2012 at 02:37:29PM +0200, Kalle Valo wrote: >> On 02/06/2012 11:06 AM, Vasanthakumar Thiagarajan wrote: >> >>> Why not to use simple_read_from_buffer()?, looks like it can also >>> takes care of len == 0 case in the following check. >>> >>> if (pos >= available || !count) >>> return 0; >>> >>> when available (len) is 0, pos = available with >>> ath6kl_fwlog_block_read(). >> >> I actually used simple_read_from_buffer() first, but the problem is that >> it assumes that there's just one buffer from which the data is copied. >> But in this case there can be multiple buffers from which I copy data. >> >> Ok, that was a bit confusing, let's try to explain a bit differently :) >> >> If 'ppos > 0' (for example during the second function call) >> simple_read_from_buffer() will try to copy from 'user_buf + ppos' but I >> would want to copy from 'user_buf'. > > I think you mean s/user_buf/buf. Correct. > Are you not making sure that the > length of the data is not more than the requested one which is > passed to copy_to_user() so that read() is always called with > *ppos=0?. The following code seems to do that But the function is called multiple times with increasing values of *ppos as more data is returned to user space: [ 100.303747] ath6kl_fwlog_block_read(): *ppos 0 [ 100.305252] ath6kl_fwlog_block_read(): *ppos 30116 [ 101.768947] ath6kl_fwlog_block_read(): *ppos 31624 [ 117.027469] ath6kl_fwlog_block_read(): *ppos 33124 [ 117.090146] ath6kl_fwlog_block_read(): *ppos 34628 [ 117.172338] ath6kl_fwlog_block_read(): *ppos 36128 So I can't assume that *ppos = 0. Kalle -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
