linux-kernel - Re: [PATCH v6 1/2] mctp pcc: Check before sending MCTP PCC response ACK

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Message-ID: <38fab0d5-8a31-41be-8426-6f180e6d4203@amperemail.onmicrosoft.com>
Date: Thu, 31 Oct 2024 20:16:44 -0400
From: Adam Young <admiyo@...eremail.onmicrosoft.com>
To: "lihuisong (C)" <lihuisong@...wei.com>, admiyo@...amperecomputing.com
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Jeremy Kerr <jk@...econstruct.com.au>,
 Matt Johnston <matt@...econstruct.com.au>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Len Brown <lenb@...nel.org>,
 "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
 Robert Moore <robert.moore@...el.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Jassi Brar <jassisinghbrar@...il.com>, Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v6 1/2] mctp pcc: Check before sending MCTP PCC response
 ACK

On 10/30/24 05:45, lihuisong (C) wrote:
>> + check_and_ack(pchan, chan);
>>       pchan->chan_in_use = false;
>>         return IRQ_HANDLED;
>> @@ -352,6 +368,9 @@ pcc_mbox_request_channel(struct mbox_client *cl, 
>> int subspace_id)
>>       if (rc)
>>           return ERR_PTR(rc);
>>   +    pchan->shmem_base_addr = devm_ioremap(chan->mbox->dev,
>> +                          pchan->chan.shmem_base_addr,
>> +                          pchan->chan.shmem_size);
> Currently, the PCC mbox client does ioremap after requesting PCC channel.
> Thus all current clients will ioremap twice. This is not good to me.
> How about add a new interface and give the type4 client the right to 
> decide whether to reply in rx_callback?

I do agree that is a cleaner implementation, but I don't have a way of 
testing the other drivers, and did not want to break them. I think your 
driver is the only that makes use of it, so we can certainly come up 
with a common approach.

The mailbox interface does not allow a return code from 
mbox_chan_received_data, which is what I originally wanted.  If that 
could return multiple status codes, one of them could indicate the need  
to send the interrupt back.  Otherwise, we need to query the driver to 
read the shared memory again.