Re: [patch] suspend: update warnings

[Nigel Cunningham]

Hi.

On Mon, 2005-08-22 at 18:15, Pavel Machek wrote:
> Update suspend documentation. Warnings were a bit overstated, and did
> not point out important stuff.
> 
> ---
> commit 790df7223ac29afec81e7201adc879973311f27e
> tree 97fa2017f8f5aded0c44cfc75ba4903fbdb7f0a4
> parent 63393fcbf056a6fd68142a49ed4e1258560dce2c
> author <pavel@amd.(none)> Mon, 22 Aug 2005 10:13:51 +0200
> committer <pavel@amd.(none)> Mon, 22 Aug 2005 10:13:51 +0200
> 
>  Documentation/power/swsusp.txt |   60 ++++++++++++++++++++++++++++++++--------
>  Documentation/power/video.txt  |    9 +++++-
>  2 files changed, 56 insertions(+), 13 deletions(-)
> 
> diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt
> --- a/Documentation/power/swsusp.txt
> +++ b/Documentation/power/swsusp.txt
> @@ -1,22 +1,20 @@
> -From kernel/suspend.c:
> +Some warnings, first.
>  
>   * BIG FAT WARNING *********************************************************
>   *
> - * If you have unsupported (*) devices using DMA...
> - *				...say goodbye to your data.
> - *
>   * If you touch anything on disk between suspend and resume...
>   *				...kiss your data goodbye.
>   *
> - * If your disk driver does not support suspend... (IDE does)
> - *				...you'd better find out how to get along
> - *				   without your data.
> - *
> - * If you change kernel command line between suspend and resume...
> - *			        ...prepare for nasty fsck or worse.
> + * If you do resume from initrd after your filesystems are mounted...
> + *				...bye bye root partition.
> + *			[this is actually same case as above]
>   *
> - * If you change your hardware while system is suspended...
> - *			        ...well, it was not good idea.
> + * If you have unsupported (*) devices using DMA, you may have some
> + * problems. If your disk driver does not support suspend... (IDE does),
> + * it may cause some problems, too. If you change kernel command line 
> + * between suspend and resume, it may do something wrong. If you change 
> + * your hardware while system is suspended... well, it was not good idea;
> + * but it wil probably only crash.

The most common driver issues I see involve:
- USB being built in or as modules that are still loaded while
suspending (getting better, but not there yet)
- DRI being used in X where the drivers don't properly support
suspend/resume (NVidia esp)
- Firewire
- CPU Freq  (improving too)

It might be good to mention these areas too.

Perhaps the 'changing your hardware' could mention that replacing faulty
hardware may be safe.

Regards,

Nigel

>   *
>   * (*) suspend/resume support is needed to make it safe.
>  
-- 
Evolution.
Enumerate the requirements.
Consider the interdependencies.
Calculate the probabilities.

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