linux-kernel - Re: [PATCH v7 03/13] PCI: Reimplement plural devres functions

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Date: Thu, 13 Jun 2024 13:45:14 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: Philipp Stanner <pstanner@...hat.com>,
	Hans de Goede <hdegoede@...hat.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Sam Ravnborg <sam@...nborg.org>, dakr@...hat.com,
	dri-devel@...ts.freedesktop.org,
	LKML <linux-kernel@...r.kernel.org>, linux-pci@...r.kernel.org
Subject: Re: [PATCH v7 03/13] PCI: Reimplement plural devres functions

On Thu, Jun 13, 2024 at 07:54:38PM +0300, Ilpo Järvinen wrote:
> On Wed, 5 Jun 2024, Philipp Stanner wrote:
> 
> > When the original PCI devres API was implemented, priority was given to
> > the creation of a set of "plural functions" such as
> > pcim_request_regions(). These functions have bit masks as parameters to
> > specify which BARs shall get mapped. Most users, however, only use those
> > to map 1-3 BARs.

> > +static int __pcim_request_region_range(struct pci_dev *pdev, int bar,
> > +		unsigned long offset, unsigned long maxlen,
> > +		const char *name, int req_flags)
> > +{
> > +	resource_size_t start = pci_resource_start(pdev, bar);
> > +	resource_size_t len = pci_resource_len(pdev, bar);
> > +	unsigned long dev_flags = pci_resource_flags(pdev, bar);
> > +
> > +	if (start == 0 || len == 0) /* That's an unused BAR. */
> > +		return 0;
> > +	if (len <= offset)
> > +		return  -EINVAL;
> 
> Extra space.

Thanks for reviewing this.  I dropped the space locally in the v9
series.

> >  void pcim_iounmap_regions(struct pci_dev *pdev, int mask)
> >  {
> > -	void __iomem * const *iomap;
> > -	int i;
> > -
> > -	iomap = pcim_iomap_table(pdev);
> > -	if (!iomap)
> > -		return;
> > +	short bar;
> 
> The current best practice is to use unsigned for loop vars that will never 
> be negative.
> 
> I don't entirely follow what is reasoning behind making it short instead 
> of unsigned int?

Existing interfaces like pcim_iomap() take "int bar".  I locally
changed all the BAR indices to "int".  We can make everything unsigned
later if worthwhile.

> > -	for (i = 0; i < PCIM_IOMAP_MAX; i++) {
> > -		if (!mask_contains_bar(mask, i))
> > +	for (bar = 0; bar < PCI_STD_NUM_BARS; bar++) {
> 
> Is this change minimal if it contains variable renames like this?
> Was "i" not "bar" even if it was given as a parameter to 
> mask_contains_bar()?

Replaced locally with "i".

Bjorn