Re: [PULL] http://linuxtv.org/hg/~dougsland/v4l-dvb

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Hi,

Am Samstag, den 07.03.2009, 19:06 -0500 schrieb Andy Walls:
> On Sat, 2009-03-07 at 18:26 -0500, Devin Heitmueller wrote:
> > On Sat, Mar 7, 2009 at 5:45 PM, Douglas Schilling Landgraf
> > <dougsland@xxxxxxxxx> wrote:
> > > Hi Mauro,
> > >
> > >    Please pull from: http://linuxtv.org/hg/~dougsland/v4l-dvb for the
> > > following:
> > >
> > >    - v4l2-apps/util: Add rewrite_eeprom tool
> > >                            Modules this script is known to work with:
> > > em28xx and saa7134
> > >
> > > Thanks,
> > > Douglas
> > > --
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> > >
> > 
> > Wow, this script really scares the crap out of me.
> 
> Actually it appears to be a meta-script.  It builds a script of i2c-set
> commands to reload an eeprom.  You then have an opportunity to review
> the script to reload the EEPROM and then run it.
> 
> You first have to load the gun, then pull the trigger an shoot yourself
> in the foot. :)
> 
> 
> >   Is this something
> > we *really* need?
> 
> No.  IMO, factory provisionsing is the purview of the manufacturer.
> Does someone actually have evidence of the Windows drivers reloading the
> eeproms on these devices if it is, in fact, true that:
> 
> "the eeprom may be erased, due to a bug on a *few eeprom* chipsets that
> sometimes considers i2c messages to other devices as being for it"
> 
> 
> But I don't have trashed eeprom sitting in front of me, and I don't have
> to build 256 i2cset commands by hand. :)
> 
> 
> 
> >    If so, it needs to have a HUGE WARNING explaining
> > the few cases that it should actually be used, and it should also
> > explicitly block usage against chipsets except for those that have
> > been validated to work.
> 
> I agree with these.
> 
> 
> > Do you really want to be responsible for the
> > first time some unknowing user runs this against cx88 or some other
> > chipset you never tried it against and it bricks their board?
> 
> Section 11 of the GPL legally absolves the authors of most, if not all,
> responsibility 
> 
>                            NO WARRANTY
> 
> 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
> FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
> OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
> PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER
> EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
> WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE
> ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH
> YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
> NECESSARY SERVICING, REPAIR OR CORRECTION.
> 
> 
> 
> 
> > Also, this won't work against newer em28xx chipsets like the em2874
> > and em2884, which have 16-bit eeproms.  And if you corrupt the eeprom
> > on the em2874, you actually *WILL* brick the device (which is why I
> > removed the code that reads the eeprom in the first place).
> 
> The script should state in big letters that EXPERT knowledge of the
> device in question is required to reduce the risk. Perhaps reiterating
> portions of section 11 of the GPL.  (But then again, what is the risk of
> a non-functioning device continuing not to function?).
> 
> 
> The real risk is running the linux code that trashes the eeprom in the
> first place.  I would look to prevent that code from running, or at
> least flag the risky condition in the kernel log.
> 
> 
> > Devin
> 
> Regards,
> Andy
> 

as far I know we never had a report about destroyed eeprom content on
the saa7134 driver, but it seems Mauro and Douglas have seen it ?

On the saa7134 I won't care that much, since currently we still can
force all settings even with an erased eeprom, but if users cause
trouble by using the script in a wrong way, their windows drivers won't
work anymore and they don't have a chance to fix them except writing
back the right eeprom content.

In the past the DScaler guys had such a trouble on the cx88xx MSI
TV@nywhere Master caused by them and they were badly in need of such a
tool.

So, in general it is good to have it, but there needs to be that
BIG RED WARNING :)

Cheers,
Hermann




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