Best practice to lock a read/write to a HW register

[binoy.jayan at wipro.com]

Hi Luca

The locking mechanism to be used depends on what your piece of code does and where your code runs. 
If your code runs in a interrupt context (inside an interrupt handler), you should use a spinlock (with irq save and restore). 
Else you can use mutex or a semaphore. 

In either cases, you don't lock the hardware register but create a lock descriptor and lock the same.
So you need to implement locking at every place the register is accessed.

Please refer http://lwn.net/Kernel/LDD3/ on how to use locks.

Regards,
Binoy Jayan



________________________________________
From: kernelnewbies-bounces at kernelnewbies.org [kernelnewbies-bounces at kernelnewbies.org] on behalf of Luca Ellero [lroluk at gmail.com]
Sent: Thursday, November 14, 2013 4:02 PM
To: kernelnewbies at kernelnewbies.org
Subject: Best practice to lock a read/write to a HW register

Hi all,
can someone please show me which is the best practice to lock a
read/write to a hardware register.
In other words if, in a driver, I want to modify a bit in a HW register,
I have to read the register, set/reset the relevant bit and write back
the reg.
But what can I do to be sure that no other code modifies the register
between my read and write?
Is spin_lock() suitable for this purpose?
Thanks
Best regards
Luca


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