linux-kernel - RE: [PATCH v10 2/6] usb:common Separated decoding functions from dwc3 driver.

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Date:   Mon, 22 Jul 2019 10:06:38 +0000
From:   Pawel Laszczak <pawell@...ence.com>
To:     Joe Perches <joe@...ches.com>,
        "felipe.balbi@...ux.intel.com" <felipe.balbi@...ux.intel.com>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "rogerq@...com" <rogerq@...com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jbergsagel@...com" <jbergsagel@...com>,
        "nsekhar@...com" <nsekhar@...com>, "nm@...com" <nm@...com>,
        Suresh Punnoose <sureshp@...ence.com>,
        Jayshri Dajiram Pawar <jpawar@...ence.com>,
        Rahul Kumar <kurahul@...ence.com>,
        Anil Joy Varughese <aniljoy@...ence.com>
Subject: RE: [PATCH v10 2/6] usb:common Separated decoding functions from dwc3
 driver.

Hi,

>
>On Sun, 2019-07-21 at 19:32 +0100, Pawel Laszczak wrote:
>> Patch moves some decoding functions from driver/usb/dwc3/debug.h driver
>> to driver/usb/common/debug.c file. These moved functions include:
>[]
>> diff --git a/drivers/usb/common/debug.c b/drivers/usb/common/debug.c
>[]
>> +static void usb_decode_set_clear_feature(__u8 bRequestType, __u8 bRequest,
>> +					 __u16 wValue, __u16 wIndex,
>> +					 char *str, size_t size)
>
>It's probably not necessary to use Hungarian
>when moving these functions into generic code.

In my opinion it's ok in this place. It's consistence with USB specification ch9 and with
https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/usb/ch9.h. (look at usb_ctrlrequest). 

>
>> +{
>> +	switch (bRequestType & USB_RECIP_MASK) {
>> +	case USB_RECIP_DEVICE:
>> +		snprintf(str, size, "%s Device Feature(%s%s)",
>> +			 bRequest == USB_REQ_CLEAR_FEATURE ? "Clear" : "Set",
>> +			 ({char *s;
>> +				switch (wValue) {
>> +				case USB_DEVICE_SELF_POWERED:
>> +					s = "Self Powered";
>> +					break;
>> +				case USB_DEVICE_REMOTE_WAKEUP:
>> +					s = "Remote Wakeup";
>> +					break;
>> +				case USB_DEVICE_TEST_MODE:
>> +					s = "Test Mode";
>> +					break;
>> +				case USB_DEVICE_U1_ENABLE:
>> +					s = "U1 Enable";
>> +					break;
>> +				case USB_DEVICE_U2_ENABLE:
>> +					s = "U2 Enable";
>> +					break;
>> +				case USB_DEVICE_LTM_ENABLE:
>> +					s = "LTM Enable";
>> +					break;
>> +				default:
>> +					s = "UNKNOWN";
>> +				} s; }),
>> +			 wValue == USB_DEVICE_TEST_MODE ?
>> +			 ({ char *s;
>> +				switch (wIndex) {
>> +				case TEST_J:
>> +					s = ": TEST_J";
>> +					break;
>> +				case TEST_K:
>> +					s = ": TEST_K";
>> +					break;
>> +				case TEST_SE0_NAK:
>> +					s = ": TEST_SE0_NAK";
>> +					break;
>> +				case TEST_PACKET:
>> +					s = ": TEST_PACKET";
>> +					break;
>> +				case TEST_FORCE_EN:
>> +					s = ": TEST_FORCE_EN";
>> +					break;
>> +				default:
>> +					s = ": UNKNOWN";
>> +				} s; }) : "");
>
>I always find this sort of embedded switch/case char *
>statement expressions difficult to read and think it's
>better to use separate lookup functions.
>

It has been changed in next patch in the series.

>I would much prefer something like:
>
>static const char *usb_device_mode_desc(u16 mode)
>{
>	switch (mode) {
>	case USB_DEVICE_SELF_POWERED:
>		return "Self Powered";
>	case USB_DEVICE_REMOTE_WAKEUP:
>		return "Remote Wakeup";
>	case USB_DEVICE_TEST_MODE:
>		return "Test Mode";
>	case USB_DEVICE_U1_ENABLE:
>		return "U1 Enable";
>	case USB_DEVICE_U2_ENABLE:
>		return "U2 Enable";
>	case USB_DEVICE_LTM_ENABLE:
>		return "LTM Enable";
>	}
>	return "UNKNOWN";
>}
>
>		snprintf(str, size, "%s Device Feature(%s%s)",
>> 			 bRequest == USB_REQ_CLEAR_FEATURE ? "Clear" : "Set",
>			 usb_device_mode_desc(wValue),
>			 etc...);
>
>
>etc...
>
Cheers,
Pawell