linux-kernel - Re: [PATCH v8 3/9] pci: Introduce pci_register_io

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Message-ID: <20140702132042.GG2173@e106497-lin.cambridge.arm.com>
Date:	Wed, 2 Jul 2014 14:20:42 +0100
From:	Liviu Dudau <Liviu.Dudau@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linux-pci <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Sinan Kaya <okaya@...eaurora.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Device Tree ML <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v8 3/9] pci: Introduce pci_register_io_range() helper
 function.

On Wed, Jul 02, 2014 at 01:38:04PM +0100, Arnd Bergmann wrote:
> Some more detailed comments now
> 
> On Tuesday 01 July 2014 19:43:28 Liviu Dudau wrote:
> > +/*
> > + * Record the PCI IO range (expressed as CPU physical address + size).
> > + * Return a negative value if an error has occured, zero otherwise
> > + */
> > +int __weak pci_register_io_range(phys_addr_t addr, resource_size_t size)
> > +{
> > +#ifdef PCI_IOBASE
> > +       struct io_range *res;
> 
> I was confused by the variable naming here: A variable named 'res' is
> normally a 'struct resource'. Maybe better call this 'range'.
> 
> > +       resource_size_t allocated_size = 0;
> > +
> > +       /* check if the range hasn't been previously recorded */
> > +       list_for_each_entry(res, &io_range_list, list) {
> > +               if (addr >= res->start && addr + size <= res->start + size)
> > +                       return 0;
> > +               allocated_size += res->size;
> > +       }
> 
> A spin_lock around the list lookup should be sufficient to get around
> the race that Will mentioned.
> 
> > +       /* range not registed yet, check for available space */
> > +       if (allocated_size + size - 1 > IO_SPACE_LIMIT)
> > +               return -E2BIG;
> 
> It might be better to limit the size to 64K if it doesn't fit at first.

Thanks Arnd for review. Will update and post a new patch soon if I don't
get any other comments.

Best regards,
Liviu

> 
> 
> 	Arnd
> 
> 

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
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