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

Greg Kroah-Hartman
2019-03-01T16:21:48Z

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@mediatek.com>
> ---
> 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 :(

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.

>
> 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