netdev - Re: [PATCH net-next v28 1/1] mctp pcc: Implement MCTP over PCC Transport

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Message-ID: <20250905-funny-amorphous-warthog-00a7a3@sudeepholla>
Date: Fri, 5 Sep 2025 15:27:36 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: Adam Young <admiyo@...eremail.onmicrosoft.com>
Cc: Adam Young <admiyo@...amperecomputing.com>,
	Jeremy Kerr <jk@...econstruct.com.au>,
	Sudeep Holla <sudeep.holla@....com>,
	Matt Johnston <matt@...econstruct.com.au>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Huisong Li <lihuisong@...wei.com>
Subject: Re: [PATCH net-next v28 1/1] mctp pcc: Implement MCTP over PCC
 Transport

On Thu, Sep 04, 2025 at 12:54:12PM -0400, Adam Young wrote:
> 
> On 9/4/25 06:48, Sudeep Holla wrote:
> > Hi Adam,
> > 
> > On Thu, Sep 04, 2025 at 12:05:42AM -0400, Adam Young wrote:
> > > Implementation of network driver for
> > > Management Control Transport Protocol(MCTP)
> > > over Platform Communication Channel(PCC)
> > > 
> > > DMTF DSP:0292
> > > https://www.dmtf.org/sites/default/files/standards/documents//
> > > DSP0292_1.0.0WIP50.pdf
> > > 
> > > MCTP devices are specified via ACPI by entries
> > > in DSDT/SDST and reference channels specified
> > > in the PCCT.  Messages are sent on a type 3 and
> > > received on a type 4 channel.  Communication with
> > > other devices use the PCC based doorbell mechanism;
> > > a shared memory segment with a corresponding
> > > interrupt and a memory register used to trigger
> > > remote interrupts.
> > > 
> > > This driver takes advantage of PCC mailbox buffer
> > > management. The data section of the struct sk_buff
> > > that contains the outgoing packet is sent to the mailbox,
> > > already properly formatted  as a PCC message.  The driver
> > > is also responsible for allocating a struct sk_buff that
> > > is then passed to the mailbox and used to record the
> > > data in the shared buffer. It maintains a list of both
> > > outging and incoming sk_buffs to match the data buffers
> > > 
> > > If the mailbox ring buffer is full, the driver stops the
> > > incoming packet queues until a message has been sent,
> > > freeing space in the ring buffer.
> > > 
> > > When the Type 3 channel outbox receives a txdone response
> > > interrupt, it consumes the outgoing sk_buff, allowing
> > > it to be freed.
> > > 
> > Sorry for not reviewing your mailbox changes in time, but I have
> > comments/concerns on the changes merged. I will respond on the original
> > thread with questions if I manage to find it, but it doesn't look good
> > at all to me. So I would want these changes to be on hold(not to be
> > merged at all).
> 
> Yeah, I was a little concerned those got merged without your input.  I will
> look for the comments.
> 

Thanks for the quick response.

-- 
Regards,
Sudeep