linux-kernel - Re: [PATCH] usb: host: ehci-sched: add comment about find

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Message-ID: <20201012002709.GA614913@rowland.harvard.edu>
Date:   Sun, 11 Oct 2020 20:27:09 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, linux-safety@...ts.elisa.tech,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH] usb: host: ehci-sched: add comment about find_tt() not
 returning error

On Sun, Oct 11, 2020 at 09:50:08PM +0100, Sudip Mukherjee wrote:
> Add a comment explaining why find_tt() will not return error even though
> find_tt() is checking for NULL and other errors.
> 
> Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@...il.com>
> ---
>  drivers/usb/host/ehci-sched.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
> index 6dfb242f9a4b..0f85aa9b2fb1 100644
> --- a/drivers/usb/host/ehci-sched.c
> +++ b/drivers/usb/host/ehci-sched.c
> @@ -244,6 +244,12 @@ static void reserve_release_intr_bandwidth(struct ehci_hcd *ehci,
>  
>  	/* FS/LS bus bandwidth */
>  	if (tt_usecs) {
> +		/*
> +		 * find_tt() will not return any error here as we have
> +		 * already called find_tt() before calling this function
> +		 * and checked for any error return. The previous call
> +		 * would have created the data structure.
> +		 */
>  		tt = find_tt(qh->ps.udev);
>  		if (sign > 0)
>  			list_add_tail(&qh->ps.ps_list, &tt->ps_list);
> @@ -1337,6 +1343,12 @@ static void reserve_release_iso_bandwidth(struct ehci_hcd *ehci,
>  			}
>  		}
>  
> +		/*
> +		 * find_tt() will not return any error here as we have
> +		 * already called find_tt() before calling this function
> +		 * and checked for any error return. The previous call
> +		 * would have created the data structure.
> +		 */
>  		tt = find_tt(stream->ps.udev);
>  		if (sign > 0)
>  			list_add_tail(&stream->ps.ps_list, &tt->ps_list);

Acked-by: Alan Stern <stern@...land.harvard.edu>