linux-kernel - Re: [PATCH 0/3] Remove scsi

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Date:   Thu, 19 Aug 2021 09:50:21 +0200
From:   Hannes Reinecke <hare@...e.de>
To:     John Garry <john.garry@...wei.com>,
        Bart Van Assche <bvanassche@....org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     satishkh@...co.com, sebaddel@...co.com, kartilak@...co.com,
        jejb@...ux.ibm.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, hch@....de
Subject: Re: [PATCH 0/3] Remove scsi_cmnd.tag

On 8/19/21 9:27 AM, John Garry wrote:
> On 19/08/2021 08:15, Hannes Reinecke wrote:
>> Hey Bart,
>>
>> Thanks for this!
>> Really helpful.
>>
>> Just a tiny wee snag:
>>
>> On 8/19/21 4:41 AM, Bart Van Assche wrote:
>>> On 8/18/21 11:08 AM, John Garry wrote:
>>>> Or maybe you or Bart have a better idea?
>>>
>>> This is how I test compilation of SCSI drivers on a SUSE system (only
>>> the cross-compilation prefix is distro specific):
>>>
>>>      # Acorn RiscPC
>>>      make ARCH=arm xconfig
>>>      # Select the RiscPC architecture (ARCH_RPC)
>>>      make -j9 ARCH=arm CROSS_COMPILE=arm-suse-linux-gnueabi- </dev/null
>>>
>>
>> Acorn RiscPC is ARMv3, which sadly isn't supported anymore with gcc9.
>> So for compilation I had to modify Kconfig to select ARMv4:
>>
> 
> Yeah, that is what I was tackling this very moment.
> 
>> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
>> index 8355c3895894..22ec9e275335 100644
>> --- a/arch/arm/mm/Kconfig
>> +++ b/arch/arm/mm/Kconfig
>> @@ -278,7 +278,7 @@ config CPU_ARM1026
>>   # SA110
>>   config CPU_SA110
>>          bool
>> -       select CPU_32v3 if ARCH_RPC
>> +       select CPU_32v4 if ARCH_RPC
> 
> Does that build fully for xconfig or any others which you tried?
> 

Yep, xconfig and full build works.

Well.

Would've worked if you hadn't messed up tag handling for acornscsi :-)

Besides: tag handling in acornscsi (and fas216, for that matter) seems 
to be completely broken.

Consider this beauty:

#ifdef CONFIG_SCSI_ACORNSCSI_TAGGED_QUEUE
        /*
         * tagged queueing - allocate a new tag to this command
         */
        if (SCpnt->device->simple_tags) {
            SCpnt->device->current_tag += 1;
            if (SCpnt->device->current_tag == 0)
                SCpnt->device->current_tag = 1;
            SCpnt->tag = SCpnt->device->current_tag;
        } else
#endif

which is broken on _soo many_ counts.
Not only does it try to allocate its own tags, the code also assumes 
that a tag value of '0' indicates that tagged queueing is not active:

static
void acornscsi_abortcmd(AS_Host *host, unsigned char tag)
{
     host->scsi.phase = PHASE_ABORTED;
     sbic_arm_write(host, SBIC_CMND, CMND_ASSERTATN);

     msgqueue_flush(&host->scsi.msgs);
#ifdef CONFIG_SCSI_ACORNSCSI_TAGGED_QUEUE
     if (tag)
         msgqueue_addmsg(&host->scsi.msgs, 2, ABORT_TAG, tag);
     else
#endif
         msgqueue_addmsg(&host->scsi.msgs, 1, ABORT);
}

And, of course, there's the usual confusion about when to check for
sdev->tagged_supported and sdev->simple_tags.

Drop me a note if I can give a hand.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@...e.de                              +49 911 74053 688
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