linux-kernel - Re: [PATCH net-next v3 2/3] net: stmmac: Add glue driver for Motorcomm YT6801 ethernet controller

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Message-ID: <aTrT3rHhtXkSyPOO@pie>
Date: Thu, 11 Dec 2025 14:23:58 +0000
From: Yao Zi <me@...ao.cc>
To: phasta@...nel.org, Bjorn Helgaas <helgaas@...nel.org>,
	"Russell King (Oracle)" <linux@...linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	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>,
	Frank <Frank.Sae@...or-comm.com>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Choong Yong Liang <yong.liang.choong@...ux.intel.com>,
	Chen-Yu Tsai <wens@...e.org>, Jisheng Zhang <jszhang@...nel.org>,
	Furong Xu <0x1207@...il.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, Mingcong Bai <jeffbai@...c.io>,
	Kexy Biscuit <kexybiscuit@...c.io>, Runhua He <hua@...c.io>,
	Xi Ruoyao <xry111@...111.site>
Subject: Re: [PATCH net-next v3 2/3] net: stmmac: Add glue driver for
 Motorcomm YT6801 ethernet controller

On Mon, Dec 08, 2025 at 10:54:36AM +0100, Philipp Stanner wrote:
> On Fri, 2025-12-05 at 16:16 -0600, Bjorn Helgaas wrote:
> > [+to Philipp, Thomas for MSI devres question]
> > 
> > On Fri, Dec 05, 2025 at 09:34:54AM +0000, Russell King (Oracle) wrote:
> > > On Fri, Dec 05, 2025 at 05:31:34AM +0000, Yao Zi wrote:
> > > > On Mon, Nov 24, 2025 at 07:06:12PM +0000, Russell King (Oracle) wrote:
> > > > > On Mon, Nov 24, 2025 at 04:32:10PM +0000, Yao Zi wrote:

...

> > > This looks very non-intuitive, and the documentation for
> > > pci_alloc_irq_vectors() doesn't help:
> > > 
> > >  * Upon a successful allocation, the caller should use pci_irq_vector()
> > >  * to get the Linux IRQ number to be passed to request_threaded_irq().
> > >  * The driver must call pci_free_irq_vectors() on cleanup.
> > >    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > > 
> > > because if what you say is correct (and it looks like it is) then this
> > > line is blatently incorrect.
> 
> True, this line is false. It should probably state "If you didn't
> enable your PCI device with pcim_enable_device(), you must call
> pci_free_irq_vectors() on cleanup."
> 
> If it's not a bug, one could keep the docu that way or at least phrase
> it in a way so that no additional users start relying on that hybrid
> mechanism.

Thanks for the clarification, would you mind me sending a patch to fix
the description, and also mention the automatic clean-up behavior
shouldn't be relied anymore in new code?

...

> The good news is that it's the last remainder of PCI hybrid devres and
> getting rid of it would allow for removal of some additional code, too
> (e.g., is_enabled bit and pcim_pin_device()).
> 
> The bad news is that it's not super trivial to remove. I looked into it
> about two times and decided I can't invest that time currently. You
> need to go over all drivers again to see who uses pcim_enable_device(),
> then add free_irq_vecs() for them all and so on…

Do you think adding an implementation of pcim_alloc_irq_vectors(), that
always call pci_free_irq_vectors() regardless whether the PCI device is
managed, will help the conversion?

This will make it more trival to rewrite drivers depending on the
automatic clean-up behavior: since calling pci_free_irq_vectors()
several times is okay, we could simply change pci_alloc_irq_vectors() to
pcim_alloc_irq_vectors(), without considering where to call
pci_free_irq_vectors().

Introducing pcim_alloc_irq_vectors() will also help newly-introduced
drivers to reduce duplicated code to handle resource clean-up.

> If you give me a pointer I can provide a TODO entry. In any case, feel
> free to set me as a reviewer!

> Regards
> Philipp

Regards,
Yao Zi