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From: Bin Meng <bmeng.cn@gmail.com>
To: u-boot@lists.denx.de
Subject: [PATCH v1 3/4] usb: usb-uclass.c: Drop le16_to_cpu() as values are already swapped
Date: Fri, 17 Jul 2020 18:11:22 +0800	[thread overview]
Message-ID: <CAEUhbmVDSRCu7iisAT55QfDDZG5mEqY9QZy+Yaig0Q5MZGOVCQ@mail.gmail.com> (raw)
In-Reply-To: <b49807f0-c0b0-410a-91a7-bcc5216eafdb@denx.de>

Hi Stefan,

On Fri, Jul 17, 2020 at 6:08 PM Stefan Roese <sr@denx.de> wrote:
>
> On 17.07.20 07:33, Bin Meng wrote:
> > Hi Stefan,
> >
> > On Thu, Jul 2, 2020 at 4:47 PM Stefan Roese <sr@denx.de> wrote:
> >>
> >> These values are already swapped to CPU endianess, so swapping them
> >
> > Can you please add more details as to when these values are swapped? I
> > assume this is inside usb_select_config() which is called before this
> > function is called?
>
> Yes. Its swapped exactly here:
>
> int usb_select_config(struct usb_device *dev)
> {
>         unsigned char *tmpbuf = NULL;
>         int err;
>
>         err = get_descriptor_len(dev, USB_DT_DEVICE_SIZE, USB_DT_DEVICE_SIZE);
>         if (err)
>                 return err;
>
>         /* correct le values */
>         le16_to_cpus(&dev->descriptor.bcdUSB);
>         le16_to_cpus(&dev->descriptor.idVendor);
>         le16_to_cpus(&dev->descriptor.idProduct);
>         le16_to_cpus(&dev->descriptor.bcdDevice);
>
> > But I wonder how this code ever worked on ARM/x86?
>
> On ARM/x86, the little-endian swapping is a no-op. So it doesn't matter
> if you swap once or twice or... ;)
>

Ah, yes! I misread this as an unconditional swap ...

> >> again is a bug. Let's remove the swap here instead.
> >>
> >> Signed-off-by: Stefan Roese <sr@denx.de>
> >> Cc: Bin Meng <bmeng.cn@gmail.com>
> >> Cc: Marek Vasut <marex@denx.de>
> >> ---
> >>
> >>   drivers/usb/host/usb-uclass.c | 8 ++++----
> >>   1 file changed, 4 insertions(+), 4 deletions(-)
> >>

Regards,
Bin

  reply	other threads:[~2020-07-17 10:11 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-02  8:47 [PATCH v1 0/4] Stefan Roese
2020-07-02  8:47 ` [PATCH v1 1/4] usb: xhci: Add missing endian conversions (cpu_to_leXX / leXX_to_cpu) Stefan Roese
2020-07-16  9:24   ` Stefan Roese
2020-07-16  9:39     ` Bin Meng
2020-07-17  5:15   ` Bin Meng
2020-07-17  9:57     ` Stefan Roese
2020-07-17 11:18   ` Bin Meng
2020-07-17 11:34     ` Stefan Roese
2020-07-17 13:46       ` Bin Meng
2020-07-17 14:04         ` [PATCH v2 " Stefan Roese
2020-07-17 14:14           ` Bin Meng
2020-07-17 18:22             ` Stefan Roese
2020-07-20  1:48               ` Bin Meng
2020-07-21  8:39                 ` Stefan Roese
2020-07-02  8:47 ` [PATCH v1 2/4] usb: xhci: xhci_mem_init: Use cpu_to_le64() and not xhci_writeq() Stefan Roese
2020-07-17  5:24   ` Bin Meng
2020-07-17 10:04     ` Stefan Roese
2020-07-17 10:09       ` Bin Meng
2020-07-17 10:11         ` Stefan Roese
2020-07-17 10:13           ` Bin Meng
2020-07-17 11:19   ` Bin Meng
2020-07-02  8:47 ` [PATCH v1 3/4] usb: usb-uclass.c: Drop le16_to_cpu() as values are already swapped Stefan Roese
2020-07-17  5:33   ` Bin Meng
2020-07-17 10:08     ` Stefan Roese
2020-07-17 10:11       ` Bin Meng [this message]
2020-07-17 11:19   ` Bin Meng
2020-07-02  8:47 ` [PATCH v1 4/4] usb: xhci: Add virt_to_phys() to support mapped platforms Stefan Roese
2020-07-17  5:57   ` Bin Meng
2020-07-17 10:17     ` Stefan Roese
2020-07-17 10:23       ` Bin Meng
2020-07-17 10:28         ` Stefan Roese
2020-07-17 10:29           ` Bin Meng
2020-07-17 10:31             ` Stefan Roese
2020-07-17 11:19   ` Bin Meng

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