How to solve this scenario in Linux device drivers

haribabu1836 · 12-05-2011, 05:56 AM

Hi All,

I have a scenario listing below, Please let me know how can i achieve this in linux.

If application program is trying to read data in a device/driver but data is not present at that moment, application should go into sleep/block state. Data came into device later and at this point of time how device/driver can tell to application or wakeup the application that now data is ready for read.

Please help me which mechanism will suitable to solve this in Linux, Thanks.

Nominal Animal · 12-05-2011, 06:38 AM

In the default case (no special open-time flags), the 'read' handler in your userspace driver should block (make the userspace thread sleep until data is available). If the userspace application has specified the O_ASYNC open()/fcntl() flag, raise a signal. If the userspace application has specified the O_NONBLOCK open()/fnctl() flag, return EWOULDBLOCK instead.

For examples, see the Linux Kernel Module Programming Guide, Blocking Processes section. There is even an example character driver in the guide.

For detailed examples on character devices, blocking and signaling, see chapters 4, 5 and 6 in Linux Device Drivers, 3rd edition.

haribabu1836 · 12-09-2011, 01:22 AM

Quote:

Originally Posted by Nominal Animal

In the default case (no special open-time flags), the 'read' handler in your userspace driver should block (make the userspace thread sleep until data is available). If the userspace application has specified the O_ASYNC open()/fcntl() flag, raise a signal. If the userspace application has specified the O_NONBLOCK open()/fnctl() flag, return EWOULDBLOCK instead.

For examples, see the Linux Kernel Module Programming Guide, Blocking Processes section. There is even an example character driver in the guide.

For detailed examples on character devices, blocking and signaling, see chapters 4, 5 and 6 in Linux Device Drivers, 3rd edition.

Thanks Nominal.