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

Amadeusz Sławiński
2024-08-06T14:57:23Z

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@quicinc.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);
>

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