See the following links: http://lxr.linux.no/source/include/linux/ppdev.h?v=2.4.21#L87 http://lxr.linux.no/source/drivers/char/ppdev.c?v=2.4.21#L442 In first link you will see the use of _IOR macro to define the ioctl command and in second link you can see how that command is handled in ioclt driver function. Similar thing can be done for _IOW, _IOWR etc. Regards, Gaurav -----Original Message----- From: kernelnewbies-bounce@xxxxxxxxxxxx [mailto:kernelnewbies-bounce@xxxxxxxxxxxx] On Behalf Of Danilo Reinhardt Sent: Tuesday, July 27, 2004 7:06 PM To: Kernel Newbies Subject: RE: _IOWR ioctl Does anyone has an working example of using _IOWR()? Am Di, den 27.07.2004 schrieb Dhiman, Gaurav um 11:52: > It is always a better idea to use copy_to_user() function for writing > something back to user space buffer. As mentioned in Rubini's books, it > take cares of all the issues related to coping across the kernel and > user space. > > If you are doing direct copying to the user buffer without any kernel > function used for this purpose, theoretically there should not be any > problem except that you can get a page fault, but in case if you are not > getting any page fault and the control is returning to user space > successfully, then there should be no problem in copying directly, but > again saying it is not a preferred way. > > Use copy_to_user() for smooth execution. > > Regards, > Gaurav. > > > -----Original Message----- > From: kernelnewbies-bounce@xxxxxxxxxxxx > [mailto:kernelnewbies-bounce@xxxxxxxxxxxx] On Behalf Of Danilo Reinhardt > Sent: Tuesday, July 27, 2004 3:02 PM > To: Kernel Newbies > Subject: _IOWR ioctl > > Hi, > > i want to use an read and write ioctl. My problem is that i dont know > what i have to do to write something back from kernel to the userland > app that has called ioctl()? > > To exchange data i've a struct with one parameter used as input for the > kernel and another as output to the userspace. > > struct st_cmd_getBridgeInfo { > __u32 bridge; // param for kernel > char info[4092]; // result to userspace > }; > > #define TIS_IOC_GETBRIDGEINFO _IOWR(0x88, 1, struct > st_cmd_getBridgeInfo) > > I guessed that i have to do it this way, but if i write something to the > info array in kernel ive got nothing at userspace. The input to kernel > works very well. Do i have to use copy_to_user or something? > > Any suggestions? > > Bye Dan > > > -- > Kernelnewbies: Help each other learn about the Linux kernel. > Archive: http://mail.nl.linux.org/kernelnewbies/ > FAQ: http://kernelnewbies.org/faq/ > -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/ -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
