linux-kernel - Re: [PATCH v24 06/34] usb: host: xhci-mem: Allow for interrupter clients to choose specific index

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Message-ID: <01bd74da-6f2d-4cea-81d0-06f8dd95b191@linux.intel.com>
Date: Tue, 6 Aug 2024 16:50:39 +0200
From: Amadeusz Sławiński
 <amadeuszx.slawinski@...ux.intel.com>
To: Wesley Cheng <quic_wcheng@...cinc.com>, srinivas.kandagatla@...aro.org,
 mathias.nyman@...el.com, perex@...ex.cz, conor+dt@...nel.org,
 corbet@....net, broonie@...nel.org, lgirdwood@...il.com, krzk+dt@...nel.org,
 Thinh.Nguyen@...opsys.com, bgoswami@...cinc.com, tiwai@...e.com,
 gregkh@...uxfoundation.org, robh@...nel.org
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 linux-sound@...r.kernel.org, linux-usb@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, linux-doc@...r.kernel.org,
 alsa-devel@...a-project.org
Subject: Re: [PATCH v24 06/34] usb: host: xhci-mem: Allow for interrupter
 clients to choose specific index

On 8/1/2024 3:17 AM, Wesley Cheng wrote:
> Some clients may operate only on a specific XHCI interrupter instance.
> Allow for the associated class driver to request for the interrupter that
> it requires.
> 
> Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>
> ---
>   drivers/usb/host/xhci-mem.c       | 29 ++++++++++++++++-------------
>   drivers/usb/host/xhci-sideband.c  |  4 ++--
>   drivers/usb/host/xhci.h           |  2 +-
>   include/linux/usb/xhci-sideband.h |  2 +-
>   4 files changed, 20 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
> index 60dfc59260d8..997e8f27acb8 100644
> --- a/drivers/usb/host/xhci-mem.c
> +++ b/drivers/usb/host/xhci-mem.c
> @@ -2340,7 +2340,7 @@ xhci_add_interrupter(struct xhci_hcd *xhci, struct xhci_interrupter *ir,
>   
>   struct xhci_interrupter *
>   xhci_create_secondary_interrupter(struct usb_hcd *hcd, unsigned int segs,
> -					u32 imod_interval)
> +					u32 imod_interval, int intr_num)
>   {
>   	struct xhci_hcd *xhci = hcd_to_xhci(hcd);
>   	struct xhci_interrupter *ir;
> @@ -2355,29 +2355,32 @@ xhci_create_secondary_interrupter(struct usb_hcd *hcd, unsigned int segs,
>   		return NULL;
>   
>   	spin_lock_irq(&xhci->lock);
> -
>   	/* Find available secondary interrupter, interrupter 0 is reserved for primary */
>   	for (i = 1; i < xhci->max_interrupters; i++) {
> -		if (xhci->interrupters[i] == NULL) {
> -			err = xhci_add_interrupter(xhci, ir, i);
> -			break;
> +		if ((intr_num > 0 && i == intr_num) || intr_num <= 0) {
> +			if (xhci->interrupters[i] == NULL) {
> +				err = xhci_add_interrupter(xhci, ir, i);
> +				if (err) {
> +					spin_unlock_irq(&xhci->lock);
> +					goto free_ir;
> +				}
> +				break;
> +			}
>   		}
>   	}

When intr_num is set, you don't really need to iterate to search for 
free slot, as you already know which one you want to use?

Wouldn't something like:
         /* Find available secondary interrupter, interrupter 0 is 
reserved for primary */
         if (!intr_num) {
                 for (i = 1; i < xhci->max_interrupters; i++) {
                         if (xhci->interrupters[i] == NULL) {
                                 err = xhci_add_interrupter(xhci, ir, i);
                                 break;
                         }
                 }
         } else {
                 if (xhci->interrupters[intr_num] == NULL)
                         err = xhci_add_interrupter(xhci, ir, i);
         }
make more sense, also make intr_num unsigned int, as it should never be 
negative as it is index into a table.

> -
>   	spin_unlock_irq(&xhci->lock);
>   
> -	if (err) {
> -		xhci_warn(xhci, "Failed to add secondary interrupter, max interrupters %d\n",
> -			  xhci->max_interrupters);
> -		xhci_free_interrupter(xhci, ir);
> -		return NULL;
> -	}
> -
>   	xhci_set_interrupter_moderation(ir, imod_interval);
> +
>   	xhci_dbg(xhci, "Add secondary interrupter %d, max interrupters %d\n",
>   		 i, xhci->max_interrupters);
>   
>   	return ir;
> +
> +free_ir:
> +	xhci_free_interrupter(xhci, ir);
> +
> +	return NULL;
>   }
>   EXPORT_SYMBOL_GPL(xhci_create_secondary_interrupter);
>   

(...)