Re: [PATCH 00/10] IOCHK interface for I/O error handling/detecting

[Matthew Wilcox]

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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