linux-kernel - Re: [RFC PATCH 02/13] ALSA: hda: hda_intel: Use always-managed version of pcim

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Message-ID: <b13b75ae16b5238ab8b6e6d6e7a0797ed8415e80.camel@redhat.com>
Date: Fri, 11 Oct 2024 14:27:48 +0200
From: Philipp Stanner <pstanner@...hat.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Damien Le Moal <dlemoal@...nel.org>, Niklas Cassel <cassel@...nel.org>, 
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Subject: Re: [RFC PATCH 02/13] ALSA: hda: hda_intel: Use always-managed
 version of pcim_intx()

On Thu, 2024-10-10 at 17:46 +0300, Andy Shevchenko wrote:
> On Wed, Oct 09, 2024 at 10:35:08AM +0200, Philipp Stanner wrote:
> > pci_intx() is a hybrid function which can sometimes be managed
> > through
> > devres. To remove this hybrid nature from pci_intx(), it is
> > necessary to
> > port users to either an always-managed or a never-managed version.
> > 
> > hda_intel enables its PCI-Device with pcim_enable_device(). Thus,
> > it needs
> > the always-managed version.
> > 
> > Replace pci_intx() with pcim_intx().
> 
> ...
> 
> >  	bus->irq = chip->pci->irq;
> >  	chip->card->sync_irq = bus->irq;
> > -	pci_intx(chip->pci, !chip->msi);
> > +	pcim_intx(chip->pci, !chip->msi);
> >  	return 0;
> 
> I believe each driver needs an individual approach. Looking at the
> above
> I would first to understand why this one is being used and why we
> can't
> switch to pci{m}_alloc_irq_vectors(). (Yeah, managed
> pci_alloc_irq_vectors()
> is probably still missing, I don't remember if you introduced it or
> not.
> 

Alright alright – we touched it in the other mail briefly, but let me
point out another specific problem:

pci_alloc_irq_vectors() *uses* pci_intx(). And pci_intx() can be
managed sometimes.

See the problem? :(

So it's not just that I couldn't port the driver Alex is concerned
about, it's also that MSI itself is a user of pci_intx().

So a pcim_alloc_irq_vectors() might end up doing double-devres or God
knows what else. Only once pci_intx() is clean one can start thinking
about the code in pci/msi/

It's the biggest reason why I want to clean it up as suggested here,
and also why the only patch I'm really nervous about is number 8.

P.