Christoph Hellwig wrote:
The structure is in ioremaped memory so you must use reads/writes to access them instead.
Yes, using read/write eliminates the compiler optimization and makes the driver portable to other architectures. That change is much more extensive, and it may be a while before I can do a major rewrite of the driver. The volatile change allows the existing driver to work. > volatile usage in drivers
is never okay - if you are accessing I/O memory you need to use proper acessors, if it is normal memory and you want atomic sematics you need to use the atomic_t type and the operators defined on it.
This is not a matter of atomicity. It is a matter of hardware DMA causing the value to change without the compiler's knowledge. If I have a DMA descriptor in normal memory (not the case in the above driver, but it is the case in another driver I maintain) that has fields that do not conform to atomic_t, using volatile seems a valid way of preventing the compiler from optimizing access to the field out of a loop. -- Paul Fulghum Microgate Systems, Ltd. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
