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    SubjectRe: [PATCH] Fix debugfs_create_file's error checking method for usb/gadget/
    Date
    From: "Alan Stern" <stern@rowland.harvard.edu>
    To: "Zhaolei" <zhaolei@cn.fujitsu.com>
    Cc: <linux-kernel@vger.kernel.org>; <dbrownell@users.sourceforge.net>; <linux-usb@vger.kernel.org>
    Sent: Friday, October 17, 2008 11:18 PM
    Subject: Re: [PATCH] Fix debugfs_create_file's error checking method for usb/gadget/


    > On Fri, 17 Oct 2008, Zhaolei wrote:
    >
    >> Hi,
    >>
    >> debugfs_create_file() returns NULL if an error occurs, returns -ENODEV
    >> when debugfs is not enabled in the kernel.
    >>
    >> Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
    >> ---
    >> drivers/usb/gadget/s3c2410_udc.c | 2 +-
    >> 1 files changed, 1 insertions(+), 1 deletions(-)
    >>
    >> diff --git a/drivers/usb/gadget/s3c2410_udc.c b/drivers/usb/gadget/s3c2410_udc.c
    >> index 29d13eb..4ba50ef 100644
    >> --- a/drivers/usb/gadget/s3c2410_udc.c
    >> +++ b/drivers/usb/gadget/s3c2410_udc.c
    >> @@ -1894,7 +1894,7 @@ static int s3c2410_udc_probe(struct platform_device *pdev)
    >> udc->regs_info = debugfs_create_file("registers", S_IRUGO,
    >> s3c2410_udc_debugfs_root,
    >> udc, &s3c2410_udc_debugfs_fops);
    >> - if (IS_ERR(udc->regs_info)) {
    >> + if (IS_ERR(udc->regs_info) || !udc->regs_info) {
    >> dev_warn(dev, "debugfs file creation failed %ld\n",
    >> PTR_ERR(udc->regs_info));
    >> udc->regs_info = NULL;
    >
    > In fact the original code and your patch are both wrong. The test
    > should simply be:
    >
    > if (!udc->regs_info) {
    > dev_warn(dev, "debugfs file creation failed\n");
    >
    Hello, Alan Stern

    If we only check if (!udc->regs_info), that is no problem except that we
    can't see dev_warn when debugfs isn't enabled in the kernel.
    It this warning message is not necessary, I agree with you.
    ->If this warning message is not necessary, I agree with you.

    Thanks!
    > (The line setting udc->regs_info to NULL can then be removed.)
    >
    > The driver should be able to work even if debugfs isn't enabled in the
    > kernel.
    >
    > Alan Stern
    >
    >
    >N²rys²¶v-ºn?S'z¶¡}²zjv¾'z?z¢s~?ÿz®¢T­¢¢"jy.A¶ÿ¶®'
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