linux-kernel - Re: [PATCH v2] PCI: Batch BAR sizing operations

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Message-ID: <20250210200819.GL32480@redhat.com>
Date: Mon, 10 Feb 2025 21:08:19 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: bhelgaas@...gle.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, mitchell.augustin@...onical.com,
	ilpo.jarvinen@...ux.intel.com
Subject: Re: [PATCH v2] PCI: Batch BAR sizing operations

On 02/10, Oleg Nesterov wrote:
>
> On 02/10, Alex Williamson wrote:
> >
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -345,7 +345,8 @@ static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom)
> >  	unsigned int pos, reg;
> >  	u16 orig_cmd;
> >
> > -	BUILD_BUG_ON(howmany > PCI_STD_NUM_BARS);
> > +	if (__builtin_constant_p(howmany))
> > +		BUILD_BUG_ON(howmany > PCI_STD_NUM_BARS);
>
> Or just
>
> 	BUILD_BUG_ON(__builtin_constant_p(howmany) && howmany > PCI_STD_NUM_BARS);
>
> I dunno... Works for me in any case.
>
> I don't know if this is "right" solution though,

I mean, atm I simply don't know if with the newer compiler
__builtin_constant_p(howmany) will be true in this case.

Oleg.