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SubjectRe: [PATCH 00/10] IOCHK interface for I/O error handling/detecting
On Thu, Jun 09, 2005 at 09:39:11PM +0900, Hidetoshi Seto wrote:
> Previously I had post two prototypes to LKML:
> 1) readX_check() interface
> Added new kin of basic readX(), which returns its result of
> I/O. But, it would not make sense that device driver have to
> check and react after each of I/Os.
> 2) clear/read_pci_errors() interface
> Added new pair-interface to sandwich I/Os. It makes sense that
> device driver can adjust the number of checking I/Os and can
> react all of them at once. However, this was not generalized,
> so I thought that more expandable design would be required.
> Today's patch is 3rd one - iochk_clear/read() interface.
> - This also adds pair-interface, but not to sandwich only readX().
> Depends on platform, starting with ioreadX(), inX(), writeX()
> if possible... and so on could be target of error checking.

It makes sense to sandwich other kinds of device accesses. I don't
think the previous clear/read_pci_errors() interface was intended *only*
to sandwich readX().

> - Additionally adds special token - abstract "iocookie" structure
> to control/identifies/manage I/Os, by passing it to OS.
> Actual type of "iocookie" could be arch-specific. Device drivers
> could use the iocookie structure without knowing its detail.

I'm not sure we need this. Surely it can be deduced from the pci_dev or
struct device?

> Expected usage(sample) is:
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> #include <linux/pci.h>
> #include <asm/io.h>
> int sample_read_with_iochk(struct pci_dev *dev, u32 *buf, int words)
> {
> unsigned long ofs = pci_resource_start(dev, 0) + DATA_OFFSET;
> int i;
> /* Create magical cookie on the stack */
> iocookie cookie;
> /* Critical section start */
> iochk_clear(&dev, &cookie);
> {
> /* Get the whole packet of data */
> for (i = 0; i < words; i++)
> *buf++ = ioread32(dev, ofs);

You do know that ioread32() doesn't take a pci_dev, right? I hope you
weren't counting on that for the rest of your implementation.

> }
> /* Critical section end. Did we have any trouble? */
> if ( iochk_read(&cookie) ) return -1;
> /* OK, all system go. */
> return 0;
> }

"Next the statesmen will invent cheap lies, putting the blame upon
the nation that is attacked, and every man will be glad of those
conscience-soothing falsities, and will diligently study them, and refuse
to examine any refutations of them; and thus he will by and by convince
himself that the war is just, and will thank God for the better sleep
he enjoys after this process of grotesque self-deception." -- Mark Twain
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