linux-kernel - Re: [PATCH v3] pata_parport: add driver (PARIDE replacement)

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Message-ID: <e843fde8-7295-dd30-6d98-a62f63d7753c@kernel.dk>
Date:   Sun, 29 Jan 2023 20:44:06 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Ondrej Zary <linux@...y.sk>
Cc:     Christoph Hellwig <hch@....de>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        Tim Waugh <tim@...erelk.net>, linux-block@...r.kernel.org,
        linux-parport@...ts.infradead.org, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] pata_parport: add driver (PARIDE replacement)

On 1/29/23 8:30?PM, Damien Le Moal wrote:
> On 1/24/23 04:09, 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.
>>
>> Unfortunately, libata drivers cannot sleep so pata_parport claims
>> parport before activating the ata host and keeps it claimed (and
>> protocol connected) until the ata host is removed. This means that
>> no devices can be chained (neither other pata_parport devices nor
>> a printer).
>>
>> paride and pata_parport are mutually exclusive because the compiled
>> protocol drivers are incompatible.
>>
>> Tested with:
>>  - Imation SuperDisk LS-120 and HP C4381A (EPAT)
>>  - Freecom Parallel CD (FRPW)
>>  - Toshiba Mobile CD-RW 2793008 w/Freecom Parallel Cable rev.903 (FRIQ)
>>  - Backpack CD-RW 222011 and CD-RW 19350 (BPCK6)
>>
>> The following bugs in low-level protocol drivers were found and will
>> be fixed later:
>>
>> 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)
>>
>> Note: EPP modes are buggy in FRPW, only modes 0 and 1 work.
>> Signed-off-by: Ondrej Zary <linux@...y.sk>
> 
> Are you going to send a patch to remove the legacy parport code ?
> If we want this queued for 6.3, it is now (this week, asap) or we will
> have to delay to 6.4. Unless Jens prefers the deprecation first, which I
> think he said "better delete now".

I would prefer if we just delete it after merging this one, in the same
release. I don't think there's any point in delaying, as we're not
removing any functionality.

You could just queue that up too when adding this patch.
 

-- 
Jens Axboe