linux-kernel - Re: [PATCH 8/9] bq27x00: Add miscdevice for each battery with ioctl for reading registers

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]

Date:	Tue, 1 Nov 2011 13:53:26 +0100
From:	Pali Rohár <pali.rohar@...il.com>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	linux-kernel@...r.kernel.org, Anton Vorontsov <cbou@...l.ru>,
	syed rafiuddin <rafiuddin.sayed@...il.com>,
	Rodolfo Giometti <giometti@...ux.it>,
	David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH 8/9] bq27x00: Add miscdevice for each battery with ioctl
 for reading registers

2011/11/1 Lars-Peter Clausen <lars@...afoo.de>:
> On 11/01/2011 01:23 PM, Pali Rohár wrote:
>> 2011/11/1 Lars-Peter Clausen <lars@...afoo.de>:
>>> On 11/01/2011 01:43 AM, Pali Rohár wrote:
>>>> * When bq27x00_battery module is loaded it take control of bq27200 i2c battery chip and then it is not possible to use i2cget program from user space (returns -EBUSY)
>>>> * This patch adds new miscdevice for each battery which has ioctl BQ27X00_READ_REG for reading battery registers from user space
>>>>
>>>> * ioctl cmd:
>>>>   #define BQ27X00_READ_REG _IO(MISC_MAJOR, 0)
>>>>
>>>> * ioctl arg:
>>>>   struct bq27x00_reg_parms {
>>>>     int reg; /* battery register (in) */
>>>>     int single; /* 1 - 8bit register, 0 - 16bit register (in) */
>>>>     int ret; /* register status, negative indicate error (out) */
>>>>   };
>>>>
>>>> Signed-off-by: Pali Rohár <pali.rohar@...il.com>
>>>
>>> I'm not sure if this is such a good idea. Why do you need to read the registers
>>> from userspace? Shouldn't all relevant information be available in a
>>> standardized format through the power_supply userspace API? If you want to use
>>> it for debugging it might be a better idea to provide a debugfs file.
>>>
>>> - Lars
>>>
>>
>> bq27200 chip has a lot of registers (for diagnostic) which is usefull
>> on Nokia N900. power_supply interface is not very abstract to handle
>> all of them.
>
> Which registers are we talking about here. And if this generally useful
> information does it make sense to add a new property to the power_supply interface?

I think it is usefull only for bq, see shell script
http://enivax.net/jk/n900/bq.tar

>
>> Also on Nokia N900 is needed proprietary pogram BME for
>> battery charging which need to access to bq27200 registers. A simple
>> LD_PRELOAD library which wrap i2c-dev access to this device provided
>> by this patch is here:
>> https://code.launchpad.net/~pali/+junk/maemo_libbqioctl
>
> Yes, but that really is a hack to work around the closed source nature of the
> BME program. I don't think we should put such hacks into the kernel.
>

Not only BME. All programs (and shell scripts and all which use
i2cget) need this interface, bacuse loading bq module will block
ic2-dev.

-- 
Pali Rohár
pali.rohar@...il.com
--
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/