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Fri, 08 May 2020 13:27:39 -0700 (PDT) Subject: Re: [PATCH] USB: host: ehci: Add error handlinginehci_mxc_drv_probe() To: Tang Bin , Greg KH Cc: stern@rowland.harvard.edu, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Zhang Shengju References: <20200508114453.15436-1-tangbin@cmss.chinamobile.com> <20200508114858.GA4085349@kroah.com> <20200508143110.GA447591@kroah.com> <107353c0-09f2-858d-2a87-498e2d8584c6@cmss.chinamobile.com> From: Sergei Shtylyov Organization: Cogent Embedded Message-ID: <66a6bbca-4218-fb71-7284-37f73d5a3c58@cogentembedded.com> Date: Fri, 8 May 2020 23:27:38 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <107353c0-09f2-858d-2a87-498e2d8584c6@cmss.chinamobile.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-MW Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/08/2020 06:03 PM, Tang Bin wrote: >>>> On Fri, May 08, 2020 at 07:44:53PM +0800, Tang Bin wrote: >>>>> The function ehci_mxc_drv_probe() does not perform sufficient error >>>>> checking after executing platform_get_irq(), thus fix it. >>>>> >>>>> Fixes: 7e8d5cd93fa ("USB: Add EHCI support for MX27 and MX31 based boards") >>>>> Signed-off-by: Zhang Shengju >>>>> Signed-off-by: Tang Bin >>>>> --- >>>>> drivers/usb/host/ehci-mxc.c | 2 ++ >>>>> 1 file changed, 2 insertions(+) >>>>> >>>>> diff --git a/drivers/usb/host/ehci-mxc.c b/drivers/usb/host/ehci-mxc.c >>>>> index a1eb5ee77..a0b42ba59 100644 >>>>> --- a/drivers/usb/host/ehci-mxc.c >>>>> +++ b/drivers/usb/host/ehci-mxc.c >>>>> @@ -50,6 +50,8 @@ static int ehci_mxc_drv_probe(struct platform_device *pdev) >>>>> } >>>>> irq = platform_get_irq(pdev, 0); >>>>> + if (irq < 0) >>>>> + return irq; >>>> <= ? >>> In the file 'drivers/base/platform.c'， the function platform_get_irq() is >>> explained and used as follows: >>> >>> * Gets an IRQ for a platform device and prints an error message if >>> finding the >>> * IRQ fails. Device drivers should check the return value for errors so >>> as to >>> * not pass a negative integer value to the request_irq() APIs. >>> * >>> * Example: >>> * int irq = platform_get_irq(pdev, 0); >>> * if (irq < 0) >>> * return irq; >>> * >>> * Return: IRQ number on success, negative error number on failure. >>> >>> And in my hardware experiment, even if I set the irq failed deliberately in >>> the DTS, the returned value is negative instead of zero. >> Please read the thread at >> https://lore.kernel.org/r/20200501224042.141366-1-helgaas%40kernel.org >> for more details about this. >> > Great, It looks beautiful, finally someone took a knife to the file 'platform.c'. I thought I did that already couple years ago, when returned 0 from platform_get_irq() could mean both IRQ # and error... :-) > > I have been studied this place for a long time, and don't know what platform can return 0, which made me curious. > > So the example should be: > > * int irq = platform_get_irq(pdev, 0); > * if (irq <= 0) > * return irq; And you then return 0 (success) as if your probe() succeeded. Congratulations! :-P > > Thanks, > > Tang Bin MBR, Sergei