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