Re: [Xen-devel] [PATCH 12/12] Unplug emulated disks and nics

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 06/17/2010 04:42 PM, Stefano Stabellini wrote:
> On Mon, 14 Jun 2010, Konrad Rzeszutek Wilk wrote:
>   
>>> +#if (defined(CONFIG_XEN_NETDEV_FRONTEND) || \
>>> +           defined(CONFIG_XEN_NETDEV_FRONTEND_MODULE)) && \
>>> +           (defined(CONFIG_XEN_PLATFORM_PCI) || \
>>> +            defined(CONFIG_XEN_PLATFORM_PCI_MODULE))
>>> +           printk(KERN_INFO "Netfront and the Xen platform PCI driver have 
>>> "
>>> +                           "been compiled for this kernel: unplug emulated 
>>> NICs.\n");
>>> +           xen_emul_unplug |= XEN_UNPLUG_ALL_NICS;
>>> +#endif
>>> +#if (defined(CONFIG_XEN_BLKDEV_FRONTEND) || \
>>> +           defined(CONFIG_XEN_BLKDEV_FRONTEND_MODULE)) && \
>>> +           (defined(CONFIG_XEN_PLATFORM_PCI) || \
>>> +            defined(CONFIG_XEN_PLATFORM_PCI_MODULE))
>>> +           printk(KERN_INFO "Blkfront and the Xen platform PCI driver have 
>>> "
>>> +                           "been compiled for this kernel: unplug emulated 
>>> disks.\n"
>>> +                           "You might have to change the root device\n"
>>> +                           "from /dev/hd[a-d] to /dev/xvd[a-d]\n"
>>> +                           "in your root= kernel command line option\n");
>>> +           xen_emul_unplug |= XEN_UNPLUG_ALL_IDE_DISKS;
>>> +#endif
>>>       
>> Wow. Can you move those checks to the header file and make it deal with
>> the #ifdef and setting of xen_emul_unplug?
>>
>>     
> I tried, but it didn't improve the elegance of the code, mainly because I
> want to keep the printk in place, so the code would look very much like
> this, but instead of being in platform-pci-unplug.c would be in
> platform_pci.h.
>   

What about using Kconfig to define an appropriate symbol and just #ifdef
on that?

>>> +   }
>>> +   /* Now unplug the emulated devices */
>>> +   if (xen_platform_pci_enabled && !(xen_emul_unplug & XEN_UNPLUG_IGNORE))
>>> +           outw(xen_emul_unplug, XEN_IOPORT_UNPLUG);
>>> +}
>>> +
>>> +static int __init parse_xen_emul_unplug(char *arg)
>>> +{
>>> +   char *p, *q;
>>> +
>>> +   for (p = arg; p; p = q) {
>>> +           q = strchr(arg, ',');
>>> +           if (q)
>>> +                   *q++ = '\0';
>>> +           if (!strcmp(p, "all"))
>>> +                   xen_emul_unplug |= XEN_UNPLUG_ALL;
>>>       
>> strncmp..
>>
>>     
> is it really needed considering that we know that both strings are NULL
> terminated and one of them is a constant?
>   

strncmp would avoid having to modify the string in place.

    J

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