linux-kernel - Re: [PATCH v7] usb: common: usb-conn-gpio: Set last role to unknown before initial detection

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Message-ID: <d5561151-08bb-9f5f-aa51-44c5ad31976b@quicinc.com>
Date:   Thu, 15 Jun 2023 19:52:32 +0530
From:   Prashanth K <quic_prashk@...cinc.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>
CC:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7] usb: common: usb-conn-gpio: Set last role to unknown
 before initial detection



On 15-06-23 03:00 pm, Greg Kroah-Hartman wrote:
> On Wed, Jun 14, 2023 at 12:14:08PM +0300, Heikki Krogerus wrote:
>> On Wed, May 31, 2023 at 08:11:14PM +0530, Prashanth K wrote:
>>> Currently if we bootup a device without cable connected, then
>>> usb-conn-gpio won't call set_role() since last_role is same as
>>> current role. This happens because during probe last_role gets
>>> initialised to zero.
>>>
>>> To avoid this, added a new constant in enum usb_role, last_role
>>> is set to USB_ROLE_UNKNOWN before performing initial detection.
>>>
>>> While at it, also handle default case for the usb_role switch
>>> in cdns3, intel-xhci-usb-role-switch & musb/jz4740 to avoid
>>> build warnings.
>>>
>>> Fixes: 4602f3bff266 ("usb: common: add USB GPIO based connection detection driver")
>>> Signed-off-by: Prashanth K <quic_prashk@...cinc.com>
>>> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
>>> ---
>>> v7: Added default case in musb/jz4740.c & intel-xhci-usb-role-switch.c to
>>>      avoid build warnings.
>>> v6: Moved USB_ROLE_UNKNOWN towards the end of enum usb_role.
>>> v5: Update commit text to mention the changes made in cdns3 driver.
>>> v4: Added Reviewed-by tag.
>>> v3: Added a default case in drivers/usb/cdns3/core.c as pointed out by
>>>      the test robot.
>>> v2: Added USB_ROLE_UNKNWON to enum usb_role.
>>>
>>>   drivers/usb/cdns3/core.c                       | 2 ++
>>>   drivers/usb/common/usb-conn-gpio.c             | 3 +++
>>>   drivers/usb/musb/jz4740.c                      | 2 ++
>>>   drivers/usb/roles/intel-xhci-usb-role-switch.c | 2 ++
>>>   include/linux/usb/role.h                       | 1 +
>>>   5 files changed, 10 insertions(+)
>>
>> Just to be clear to everybody, that USB_ROLE_UNKNOWN is not handled in
>> drivers/usb/roles/class.c, so this patch is broken.
>>
>> But the whole approach is wrong. That USB_ROLE_UNKNOWN is clearly a
>> flag where the other values in enum usb_role are actual switch states.
>> So it does not belong there.
>>
>> In general, adding globals states like that just in order to work
>> around issues in single drivers is never a good idea IMO.
> 
> Ok, let me go revert this from my tree, thanks for the review.
> 
> greg k-h

In that case, can I resubmit v1 of this patch again, where I have used a 
macro in usb-conn-gpio driver ? something like this.

@@ -27,6 +27,8 @@
  #define USB_CONN_IRQF	\
  	(IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING | IRQF_ONESHOT)

+#define USB_ROLE_UNKNOWN (USB_ROLE_NONE -1)
+
  struct usb_conn_info {
  	struct device *dev;
  	struct usb_role_switch *role_sw;
@@ -257,6 +259,9 @@  static int usb_conn_probe(struct platform_device *pdev)
  	platform_set_drvdata(pdev, info);
  	device_set_wakeup_capable(&pdev->dev, true);

+	/* Set last role to unknown before performing the initial detection */
+	info->last_role = USB_ROLE_UNKNOWN;
+
  	/* Perform initial detection */
  	usb_conn_queue_dwork(info, 0);

Thanks,
Prashanth K