Re: [Qemu-devel] [PATCH] block/raw-posix: use a character device if a block device is given

[Christoph Egger <Christoph.Egger@amd.com>]

On 05/24/11 11:10, Kevin Wolf wrote:
> Am 24.05.2011 10:36, schrieb Christoph Egger:
>> On 05/23/11 16:11, Kevin Wolf wrote:
>>> Am 23.05.2011 14:34, schrieb Christoph Egger:
>>>>
>>>> if given a block device, use the character device instead.
>>>>
>>>> From: Manuel Bouyer<bouyer@NetBSD.org>
>>>> Signed-off-by: Christoph Egger<Christoph.Egger@amd.com>
>>>
>>> A useful commit message would explain why you're doing that.
>>
>> How about this:
>>
>> On NetBSD, the PV backend has to use the block device; but a
>> userland process is better with the character device interface. In
>> addition, a block device can't be opened twice; if the backend opens
>> it qemu can't and vice-versa.
>
> Hm, what PV backend? Are you talking about Xen? If so, let's make this
> clear:

Yes, it is about Xen.

> On NetBSD a userland process is better with the character device
> interface. In addition, a block device can't be opened twice; if a Xen
> backend opens it, qemu can't and vice-versa.
>
>>>> diff --git a/block/raw-posix.c b/block/raw-posix.c
>>>> index 6b72470..d05f373 100644
>>>> --- a/block/raw-posix.c
>>>> +++ b/block/raw-posix.c
>>>> @@ -136,11 +143,45 @@ static int64_t raw_getlength(BlockDriverState *bs);
>>>>     static int cdrom_reopen(BlockDriverState *bs);
>>>>     #endif
>>>>
>>>> +#if defined(__NetBSD__)
>>>> +static const char *raw_get_rawdevice(const char *filename)
>>>> +{
>>>> +    static char namebuf[PATH_MAX];
>>>> +    const char *dp = strrchr(filename, '/');
>>>> +
>>>> +    if (dp == NULL) {
>>>> +        snprintf(namebuf, PATH_MAX, "r%s", filename);
>>>> +    } else {
>>>> +        snprintf(namebuf, PATH_MAX, "%.*s/r%s",
>>>> +            (int)(dp - filename), filename, dp + 1);
>>>> +    }
>>>> +    fprintf(stderr, "%s is a block device", filename);
>>>> +    filename = namebuf;
>>>> +    fprintf(stderr, ", using %s\n", filename);
>>>
>>> Not sure if fprintf is a good idea here, but ok.
>>
>> I want to make it clear what file the qemu process has been
>> using. this is what log files are for, isn't it ?
>
> Yeah, while I don't like fprintfs in block driver code, I do agree that
> it makes some sense here.
>
> Kevin
>


-- 
---to satisfy European Law for business letters:
Advanced Micro Devices GmbH
Einsteinring 24, 85689 Dornach b. Muenchen
Geschaeftsfuehrer: Alberto Bozzo, Andrew Bowd
Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632