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From: Andreas Bauer <andreas.bauer.nexus@gmail.com>
To: linux-usb@vger.kernel.org
Subject: [PATCH] usb: gadget/legacy/ether: assume saner default power mode
Date: Thu, 16 Sep 2021 21:56:15 +0700	[thread overview]
Message-ID: <YUNbDyoTPa+5J9Od@ws2> (raw)


I propose the included patch to the OTG USB ethernet gadget code:

  Report default of bus powered and 500mA bMaxPower consumption.

Reason:

  The USB spec requires all devices consuming more than 100mA from
  the bus to report in this manner. Devices such as Rpi Zero can operate
  in this mode and will then falsly report being self-powered when they
  are not.

  The more sane default is to report being 500mA bus-powered than being
  self-powered

This patch was born from an issue within the Raspberry Pi Zero ecosystem,
therefore I would invite comment regarding other usage of this OTG code.

Best regards,

Andreas

$ diff -u linux-5.14.2/drivers/usb/gadget/legacy/ether.c.orig linux-5.14.2/drivers/usb/gadget/legacy/ether.c
--- linux-5.14.2/drivers/usb/gadget/legacy/ether.c.orig	2021-09-08 13:52:41.000000000 +0700
+++ linux-5.14.2/drivers/usb/gadget/legacy/ether.c	2021-09-16 21:25:06.782958554 +0700
@@ -296,7 +296,8 @@
 	/* .label = f(hardware) */
 	.bConfigurationValue	= 1,
 	/* .iConfiguration = DYNAMIC */
-	.bmAttributes		= USB_CONFIG_ATT_SELFPOWER,
+	.bmAttributes		= 0,   /* bus powered implied */
+	.bMaxPower		= 250, /* 500mA in 2mA units */
 };
 
 /*-------------------------------------------------------------------------*/

             reply	other threads:[~2021-09-16 14:56 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-16 14:56 Andreas Bauer [this message]
2021-09-16 15:36 ` [PATCH] usb: gadget/legacy/ether: assume saner default power mode Greg KH
2021-09-17  5:28 ` Felipe Balbi
2021-09-17  7:15   ` Andreas Bauer
2021-09-17  8:29     ` Felipe Balbi
2021-09-17 17:12       ` Andreas Bauer

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