linux-kernel - Re: [PATCH v2 3/3] i2c / ACPI: add ACPI enumeration support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20121116144256.55b49cae@endymion.delvare>
Date:	Fri, 16 Nov 2012 14:42:56 +0100
From:	Jean Delvare <khali@...ux-fr.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	ben-linux@...ff.org, w.sang@...gutronix.de,
	linux-kernel@...r.kernel.org, lenb@...nel.org,
	rafael.j.wysocki@...el.com, broonie@...nsource.wolfsonmicro.com,
	grant.likely@...retlab.ca, linus.walleij@...aro.org,
	bhelgaas@...gle.com, mathias.nyman@...ux.intel.com,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2 3/3] i2c / ACPI: add ACPI enumeration support

On Fri, 16 Nov 2012 14:21:54 +0100, Rafael J. Wysocki wrote:
> On Friday, November 16, 2012 02:03:57 PM Jean Delvare wrote:
> > Hi Rafael,
> > 
> > On Fri, 16 Nov 2012 11:09:03 +0100, Rafael J. Wysocki wrote:
> > > On Thursday, November 15, 2012 01:03:17 PM Mika Westerberg wrote:
> > > > ACPI 5 introduced I2cSerialBus resource that makes it possible to enumerate
> > > > and configure the I2C slave devices behind the I2C controller. This patch
> > > > adds helper functions to support I2C slave enumeration.
> > > > 
> > > > An ACPI enabled I2C controller driver only needs to call acpi_i2c_register_devices()
> > > > in order to get its slave devices enumerated, created and bound to the
> > > > corresponding ACPI handle.
> > > > 
> > > > Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> > > 
> > > Are there any objections against this patch or comments?
> > > 
> > > Worfram? Jean? Ben?
> > 
> > I am no longer maintaining the i2c subsystem and will not have the time
> > to look deeply into this. All I can say is that I very happy to see
> > this finally happen. Maybe with ACPI 5.0 we will finally be done with
> > resource conflicts plaguing many systems for several years now.
> > 
> > I took a quick look, and the only thing which seems suspicious is this
> > function:
> > 
> > > +static int acpi_i2c_find_child_address(struct acpi_resource *ares, void *data)
> > > +{
> > > +	struct acpi_resource_i2c_serialbus *sb;
> > > +	struct acpi_i2c_find *i2c_find = data;
> > > +
> > > +	if (ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS)
> > > +		return 1;
> > > +
> > > +	sb = &ares->data.i2c_serial_bus;
> > > +	if (sb->type != ACPI_RESOURCE_SERIAL_TYPE_I2C)
> > > +		return 1;
> > > +
> > > +	if (sb->slave_address == i2c_find->addr)
> > 
> > The 7-bit and 10-bit address maps overlap, so the above isn't enough.
> > You must compare the addresses _and_ sb->access_mode with
> > i2c_find->access_mode (which needs to be added and filled properly.)
> > 
> > > +		i2c_find->found = true;
> > > +
> > > +	return 1;
> > > +}
> > 
> > Plus, it seems odd that this function always returns 1.
> 
> Yes, this is a bug I think.  Mika?

The equivalent function for SPI devices does the same, so if this is a
bug, it must be fixed there too. If this is not a bug then it is
questionable why these functions return something in the first place.

But then again I didn't look into the design, so I may be missing
something.

-- 
Jean Delvare
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/