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<div class="gmail_quote">On Jan 18, 2008 7:22 PM, Jenkins, Clive <<a href="mailto:Clive.Jenkins@xerox.com">Clive.Jenkins@xerox.com</a>> wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">> From: linuxppc-embedded-bounces+clive.jenkins=<a href="mailto:xerox.com@ozlabs.org">xerox.com@ozlabs.org
</a><br>> [mailto:<a href="mailto:linuxppc-embedded-bounces+clive.jenkins=xerox.com@ozlabs.org">linuxppc-embedded-bounces+clive.jenkins=xerox.com@ozlabs.org</a>]<br>> On Behalf Of Ramkumar J<br>> Sent: 18 January 2008 10:54
<br>> To: <a href="mailto:linuxppc-embedded@ozlabs.org">linuxppc-embedded@ozlabs.org</a><br>> Subject: Adding new driver in Linux 2.6 - read fails with -1<br>
<div class="Ih2E3d">><br>> Hi All,<br>><br>> I m using the Linux 2.6(2.6.23-rc2) from Grants for ML-403 and<br>> I tried to add a new driver for a hardware based stream.<br></div>> [...] For read, the function doesnt seem calling the drivers read
<br>> routine and exits with -1. [...]<br><br>You are not giving enough information -- better to supply the complete<br>code of driver and application, and the complete kernel log, or put<br>them on a web/ftp site and supply pointers to them.
<br><br>When your application calls read(), I cannot see whether you are<br>passing a valid file descriptor, whether you have opened the device<br>etc. You say read() returns -1, but you don't give the value of errno
<br>or the error string corresponding to that value. An easy way to get<br>this is to use perror() in your app.<br>
<div class="Ih2E3d"><br>> /* Wait while empty. */<br>> while (((status=readl( ((volatile unsigned char*)<br>remapped_address)<br>> + 8)&3))==0)<br><br></div>One thing I can see is that you have a "busy wait" loop in your
<br>driver's read method. This will waste CPU time and may hang<br>indefinitely. Better to use wait-event_interruptible, and check for<br>termination of the wait by unexpected events such as signals and<br>changes of power management state.
<br><font color="#888888"><br>Clive<br></font></blockquote></div>
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<div>Hi,</div>
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<div>Thanks a lot for replying. I will try using the perror() function and modify the busy-loop through wait-for functions. Also, the way I have accessed the memory mapped IO, is to ioremap() the physical address and then use readl() functions. Is this correct.
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<div>Following is the link to the driver file,</div>
<div><a href="http://www.geocities.com/ramkumarj_2000/impulse-stream.c">http://www.geocities.com/ramkumarj_2000/impulse-stream.c</a></div>
<div><a href="http://www.geocities.com/ramkumarj_2000/1.txt">http://www.geocities.com/ramkumarj_2000/1.txt</a> as impulse-stream.h<br></div>
<div>This is intermediate layer and part of my application space,</div>
<div><a href="http://www.geocities.com/ramkumarj_2000/co_stream_linux.c">http://www.geocities.com/ramkumarj_2000/co_stream_linux.c</a></div>
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<div>The application is,</div>
<div><a href="http://www.geocities.com/ramkumarj_2000/HelloWorld.c">http://www.geocities.com/ramkumarj_2000/HelloWorld.c</a></div>
<div><a href="http://www.geocities.com/ramkumarj_2000/HelloWorld_sw.c">http://www.geocities.com/ramkumarj_2000/HelloWorld_sw.c</a></div>
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<div>Logs at,</div>
<div><a href="http://www.geocities.com/ramkumarj_2000/logs.txt">http://www.geocities.com/ramkumarj_2000/logs.txt</a></div>
<div><a href="http://www.geocities.com/ramkumarj_2000/kernellog.txt">http://www.geocities.com/ramkumarj_2000/kernellog.txt</a></div>
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<div>My apologies for the dirty code. To add some background, it starts from the main() in HelloWorld.c and it proceeds calling the hear_hello() in HelloWorld_sw.c . The co_stream_* functions are defined in intermediate layer co_stream_linux.c and co_stream_open is defined to nothing in one header file. The open and ioctl call ( modified a little in the driver now for debugging) map from co_stream_attach.
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<div>co_stream_read is read and co_stream_write is the write to driver.</div>
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<div>Though the logs indicate the call of release function before the read, I m not quite sure about this as the read not being called have failed to get inside the kernel messages.</div>
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<div>Thanks and Regards,</div>
<div>Ramkumar.</div>