Hello,
had anybody considered implementing a toggle switch for the "sd" driver that would send a different write command code, than the standard Write?
The one I would need instead of Write is the Write-And-Verify and it comes in various control block size flavors of course.
There are some drives, or more precisely - normal drives with a custom firmware, that simply reject a regular Write - likely as not being good enough for the intended high-rel application - which I can understand, but even after reformatting the drive to no-PI and going to "poor" 512B sector
size, they still refuse to do an easy Write operation. I had verified that by using the sg_write_verify (that uses an ioctl) I can really write data to these drives. The reading path is working okay and both dd and hdparm works at expected speeds.
I had a look in the source code, and it seems that making such change would need just a new binary flag per drive - and the most complicated thing being the actual auto-detection of such an "enhanced to being picky" firmware. Initially I could live with the flag exposed on sysfs, and set it up
by an udev based user-space script that activates on drive detection/hot-plug.
A better one could preset the flag based on model names - but the list will be long and hard to maintain in-kernel, while a try-write,retry-writeverify like auto-detection at first occurrence of a write needs to handle various expected and unexpected errors and I do not see it as a clean thing
for the kernel.
Anyone up to the task?
Or if I do it myself and send here some patches, what to be aware of?
Daniel
