_IOR('t',90,int)

Sarada prasanna (csaradap@mihy.mot.com)
Thu, 16 Aug 2001 07:57:09 +0530


Hi friends,
While reading a source code of pppd i came across a macro
declaration
like

#define PPPIOCGFLAGS _IOR('t', 90, int) /* get configuration flags
*/

I refered to the book called "Linux kernel internals by Beck and others" and
on
the page 219 (chap implementing a device driver) i found out the line
telling

_IOR(c,d,t) for commands which write back to the user address space a
value of
the C type t

but still i am not being able to understand the macro declaration. Can
someone
kindly tell me about the _IOW

thanx

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Choudhury Sarada Prasanna Nanda
Trainee T:24
Motorola India Electronics
TSR Towers, Raj Bhavan Road
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<csaradap@mihy.mot.com <mailto:csaradap@mihy.mot.com>>
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