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SubjectRe: [PATCH] pata_parport: add driver (PARIDE replacement)
On 3/13/22 1:15 PM, Ondrej Zary wrote:
> On Saturday 12 March 2022 15:44:15 Ondrej Zary wrote:
>> The pata_parport is a libata-based replacement of the old PARIDE
>> subsystem - driver for parallel port IDE devices.
>> It uses the original paride low-level protocol drivers but does not
>> need the high-level drivers (pd, pcd, pf, pt, pg). The IDE devices
>> behind parallel port adapters are handled by the ATA layer.
>> This will allow paride and its high-level drivers to be removed.
>> paride and pata_parport are mutually exclusive because the compiled
>> protocol drivers are incompatible.
>> Tested with Imation SuperDisk LS-120 and HP C4381A (both use EPAT
>> chip).
>> Note: EPP-32 mode is buggy in EPAT - and also in all other protocol
>> drivers - they don't handle non-multiple-of-4 block transfers
>> correctly. This causes problems with LS-120 drive.
>> There is also another bug in EPAT: EPP modes don't work unless a 4-bit
>> or 8-bit mode is used first (probably some initialization missing?).
>> Once the device is initialized, EPP works until power cycle.
>> So after device power on, you have to:
>> echo "parport0 epat 0" >/sys/bus/pata_parport/new_device
>> echo pata_parport.0 >/sys/bus/pata_parport/delete_device
>> echo "parport0 epat 4" >/sys/bus/pata_parport/new_device
>> (autoprobe will initialize correctly as it tries the slowest modes
>> first but you'll get the broken EPP-32 mode)
> Found a bug - the same device can be registered multiple times. Fix
> will be in v2. But this revealed a bigger problem: pi_connect can
> sleep (uses parport_claim_or_block) and libata does not like that. Any
> ideas how to fix this?

I think you'd need two things here:

- The blk-mq queue should be registered with BLK_MQ_F_BLOCKING, which
will allow blocking off the queue_rq path.

- You need to look at making libata safe wrt calling ata_qc_issue()
outside the lock. Should probably be fine if you just gate that on
whether or not the queue was setup in blocking mode, as that doesn't
currently exist in libata.

Jens Axboe

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