Re: [PATCH] usb: introduce usb_ep_type_string() function

[Chunfeng Yun]

Hi,
On Fri, 2019-03-01 at 17:21 +0100, Greg Kroah-Hartman wrote:
> On Fri, Mar 01, 2019 at 02:58:23PM +0800, Chunfeng Yun wrote:
> > In some places, the code prints a human-readable USB endpoint
> > transfer type (e.g. "bulk"). This involves a switch statement
> > sometimes wrapped around in ({ ... }) block leading to code
> > repetition.
> > To make this scenario easier, here introduces usb_ep_type_string()
> > function, which returns a human-readable name of provided
> > endpoint type.
> > It also changes a few places switch was used to use this
> > new function.
> > 
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>
> > ---
> >  drivers/usb/common/common.c              | 16 ++++++++++++++++
> >  drivers/usb/core/endpoint.c              | 18 ++----------------
> >  drivers/usb/core/hcd.c                   | 17 ++---------------
> >  drivers/usb/dwc3/debugfs.c               | 23 ++++-------------------
> >  drivers/usb/gadget/udc/aspeed-vhub/epn.c |  6 +-----
> >  drivers/usb/gadget/udc/dummy_hcd.c       | 16 +---------------
> >  drivers/usb/host/xhci-trace.h            | 19 ++-----------------
> >  include/linux/usb/ch9.h                  |  8 ++++++++
> >  8 files changed, 36 insertions(+), 87 deletions(-)
> > 
> > diff --git a/drivers/usb/common/common.c b/drivers/usb/common/common.c
> > index 48277bbc15e4..2174dd9ec176 100644
> > --- a/drivers/usb/common/common.c
> > +++ b/drivers/usb/common/common.c
> > @@ -16,6 +16,22 @@
> >  #include <linux/usb/otg.h>
> >  #include <linux/of_platform.h>
> >  
> > +static const char *const ep_type_names[] = {
> > +	[USB_ENDPOINT_XFER_CONTROL] = "ctrl",
> > +	[USB_ENDPOINT_XFER_ISOC] = "isoc",
> > +	[USB_ENDPOINT_XFER_BULK] = "bulk",
> > +	[USB_ENDPOINT_XFER_INT] = "intr",
> > +};
> > +
> > +const char *usb_ep_type_string(int ep_type)
> > +{
> > +	if (ep_type < 0 || ep_type >= ARRAY_SIZE(ep_type_names))
> > +		return "unknown";
> > +
> > +	return ep_type_names[ep_type];
> > +}
> > +EXPORT_SYMBOL_GPL(usb_ep_type_string);
> > +
> >  const char *usb_otg_state_string(enum usb_otg_state state)
> >  {
> >  	static const char *const names[] = {
> > diff --git a/drivers/usb/core/endpoint.c b/drivers/usb/core/endpoint.c
> > index 1c2c04079676..afa43f9a47b2 100644
> > --- a/drivers/usb/core/endpoint.c
> > +++ b/drivers/usb/core/endpoint.c
> > @@ -60,23 +60,9 @@ static ssize_t type_show(struct device *dev, struct device_attribute *attr,
> >  			 char *buf)
> >  {
> >  	struct ep_device *ep = to_ep_device(dev);
> > -	char *type = "unknown";
> > +	int ep_type = usb_endpoint_type(ep->desc);
> >  
> > -	switch (usb_endpoint_type(ep->desc)) {
> > -	case USB_ENDPOINT_XFER_CONTROL:
> > -		type = "Control";
> > -		break;
> > -	case USB_ENDPOINT_XFER_ISOC:
> > -		type = "Isoc";
> > -		break;
> > -	case USB_ENDPOINT_XFER_BULK:
> > -		type = "Bulk";
> > -		break;
> > -	case USB_ENDPOINT_XFER_INT:
> > -		type = "Interrupt";
> > -		break;
> > -	}
> > -	return sprintf(buf, "%s\n", type);
> > +	return sprintf(buf, "%s\n", usb_ep_type_string(ep_type));
> 
> You just changed a user/kernel API here, the strings are now different
> from what they used to be :(
How about using these type string to keep them unchanged?

I need help from Felipe and Mathias to check whether the changes in dwc3
and xhci have side effect or not, and waiting for their comments

Thanks
> 
> That's not ok, odds are you will break tools if you do this.
> 
> >  }
> >  static DEVICE_ATTR_RO(type);
> >  
> > diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> > index 015b126ce455..193ee92b2fdb 100644
> > --- a/drivers/usb/core/hcd.c
> > +++ b/drivers/usb/core/hcd.c
> > @@ -1875,23 +1875,10 @@ void usb_hcd_flush_endpoint(struct usb_device *udev,
> >  		/* kick hcd */
> >  		unlink1(hcd, urb, -ESHUTDOWN);
> >  		dev_dbg (hcd->self.controller,
> > -			"shutdown urb %pK ep%d%s%s\n",
> > +			"shutdown urb %pK ep%d%s-%s\n",
> >  			urb, usb_endpoint_num(&ep->desc),
> >  			is_in ? "in" : "out",
> > -			({	char *s;
> > -
> > -				 switch (usb_endpoint_type(&ep->desc)) {
> > -				 case USB_ENDPOINT_XFER_CONTROL:
> > -					s = ""; break;
> > -				 case USB_ENDPOINT_XFER_BULK:
> > -					s = "-bulk"; break;
> > -				 case USB_ENDPOINT_XFER_INT:
> > -					s = "-intr"; break;
> > -				 default:
> > -					s = "-iso"; break;
> > -				};
> > -				s;
> > -			}));
> > +			usb_ep_type_string(usb_endpoint_type(&ep->desc)));
> 
> You also changed the message here for control endpoints, but that's not
> a big deal, it's ok.
> 
> >  		usb_put_urb (urb);
> >  
> >  		/* list contents may have changed */
> > diff --git a/drivers/usb/dwc3/debugfs.c b/drivers/usb/dwc3/debugfs.c
> > index 1c792710348f..d9e2a63835fe 100644
> > --- a/drivers/usb/dwc3/debugfs.c
> > +++ b/drivers/usb/dwc3/debugfs.c
> > @@ -750,28 +750,13 @@ static int dwc3_transfer_type_show(struct seq_file *s, void *unused)
> >  	unsigned long		flags;
> >  
> >  	spin_lock_irqsave(&dwc->lock, flags);
> > -	if (!(dep->flags & DWC3_EP_ENABLED) ||
> > -			!dep->endpoint.desc) {
> > -		seq_printf(s, "--\n");
> > +	if (!(dep->flags & DWC3_EP_ENABLED) || !dep->endpoint.desc) {
> > +		seq_puts(s, "unknown\n");
> >  		goto out;
> >  	}
> >  
> > -	switch (usb_endpoint_type(dep->endpoint.desc)) {
> > -	case USB_ENDPOINT_XFER_CONTROL:
> > -		seq_printf(s, "control\n");
> > -		break;
> > -	case USB_ENDPOINT_XFER_ISOC:
> > -		seq_printf(s, "isochronous\n");
> > -		break;
> > -	case USB_ENDPOINT_XFER_BULK:
> > -		seq_printf(s, "bulk\n");
> > -		break;
> > -	case USB_ENDPOINT_XFER_INT:
> > -		seq_printf(s, "interrupt\n");
> > -		break;
> > -	default:
> > -		seq_printf(s, "--\n");
> > -	}
> > +	seq_printf(s, "%s\n",
> > +		   usb_ep_type_string(usb_endpoint_type(dep->endpoint.desc)));
> 
> It is debugfs, so no real API guarantees at all, but you did change the
> output format, and that's not always good.
got it
> 
> >  
> >  out:
> >  	spin_unlock_irqrestore(&dwc->lock, flags);
> > diff --git a/drivers/usb/gadget/udc/aspeed-vhub/epn.c b/drivers/usb/gadget/udc/aspeed-vhub/epn.c
> > index 4a28e3fbeb0b..165b0a43670e 100644
> > --- a/drivers/usb/gadget/udc/aspeed-vhub/epn.c
> > +++ b/drivers/usb/gadget/udc/aspeed-vhub/epn.c
> > @@ -593,10 +593,6 @@ static int ast_vhub_epn_disable(struct usb_ep* u_ep)
> >  static int ast_vhub_epn_enable(struct usb_ep* u_ep,
> >  			       const struct usb_endpoint_descriptor *desc)
> >  {
> > -	static const char *ep_type_string[] __maybe_unused = { "ctrl",
> > -							       "isoc",
> > -							       "bulk",
> > -							       "intr" };
> >  	struct ast_vhub_ep *ep = to_ast_ep(u_ep);
> >  	struct ast_vhub_dev *dev;
> >  	struct ast_vhub *vhub;
> > @@ -646,7 +642,7 @@ static int ast_vhub_epn_enable(struct usb_ep* u_ep,
> >  	ep->epn.wedged = false;
> >  
> >  	EPDBG(ep, "Enabling [%s] %s num %d maxpacket=%d\n",
> > -	      ep->epn.is_in ? "in" : "out", ep_type_string[type],
> > +	      ep->epn.is_in ? "in" : "out", usb_ep_type_string(type),
> >  	      usb_endpoint_num(desc), maxpacket);
> >  
> >  	/* Can we use DMA descriptor mode ? */
> > diff --git a/drivers/usb/gadget/udc/dummy_hcd.c b/drivers/usb/gadget/udc/dummy_hcd.c
> > index baf72f95f0f1..40c6a484e232 100644
> > --- a/drivers/usb/gadget/udc/dummy_hcd.c
> > +++ b/drivers/usb/gadget/udc/dummy_hcd.c
> > @@ -617,21 +617,7 @@ static int dummy_enable(struct usb_ep *_ep,
> >  		_ep->name,
> >  		desc->bEndpointAddress & 0x0f,
> >  		(desc->bEndpointAddress & USB_DIR_IN) ? "in" : "out",
> > -		({ char *val;
> > -		 switch (usb_endpoint_type(desc)) {
> > -		 case USB_ENDPOINT_XFER_BULK:
> > -			 val = "bulk";
> > -			 break;
> > -		 case USB_ENDPOINT_XFER_ISOC:
> > -			 val = "iso";
> > -			 break;
> > -		 case USB_ENDPOINT_XFER_INT:
> > -			 val = "intr";
> > -			 break;
> > -		 default:
> > -			 val = "ctrl";
> > -			 break;
> > -		 } val; }),
> > +		usb_ep_type_string(usb_endpoint_type(desc)),
> >  		max, ep->stream_en ? "enabled" : "disabled");
> >  
> >  	/* at this point real hardware should be NAKing transfers
> > diff --git a/drivers/usb/host/xhci-trace.h b/drivers/usb/host/xhci-trace.h
> > index 88b427434bd8..bac73d688f11 100644
> > --- a/drivers/usb/host/xhci-trace.h
> > +++ b/drivers/usb/host/xhci-trace.h
> > @@ -289,23 +289,8 @@ DECLARE_EVENT_CLASS(xhci_log_urb,
> >  	),
> >  	TP_printk("ep%d%s-%s: urb %p pipe %u slot %d length %d/%d sgs %d/%d stream %d flags %08x",
> >  			__entry->epnum, __entry->dir_in ? "in" : "out",
> > -			({ char *s;
> > -			switch (__entry->type) {
> > -			case USB_ENDPOINT_XFER_INT:
> > -				s = "intr";
> > -				break;
> > -			case USB_ENDPOINT_XFER_CONTROL:
> > -				s = "control";
> > -				break;
> > -			case USB_ENDPOINT_XFER_BULK:
> > -				s = "bulk";
> > -				break;
> > -			case USB_ENDPOINT_XFER_ISOC:
> > -				s = "isoc";
> > -				break;
> > -			default:
> > -				s = "UNKNOWN";
> > -			} s; }), __entry->urb, __entry->pipe, __entry->slot_id,
> > +			usb_ep_type_string(__entry->type),
> > +			__entry->urb, __entry->pipe, __entry->slot_id,
> >  			__entry->actual, __entry->length, __entry->num_mapped_sgs,
> >  			__entry->num_sgs, __entry->stream, __entry->flags
> >  		)
> 
> Another api change with "control" :(
> 
> I like the idea, but you can not break user/kernel apis like this
> without knowing the affects that could happen.
> 
> thanks,
> 
> greg k-h