Subject: Re: [PATCH v3 01/12] usb: xhci: add sysfs file for xHCI debug port
To: Dave Young <dyoung@redhat.com>
References: <1447054721-7390-1-git-send-email-baolu.lu@linux.intel.com>
 <1447054721-7390-2-git-send-email-baolu.lu@linux.intel.com>
 <20151110093634.GA22332@localhost.localdomain>
Cc: Mathias Nyman <mathias.nyman@intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Alan Stern <stern@rowland.harvard.edu>, linux-usb@vger.kernel.org,
        x86@kernel.org, linux-kernel@vger.kernel.org
From: "Lu, Baolu" <baolu.lu@linux.intel.com>
Message-ID: <5642A20F.9020407@linux.intel.com>
Date: Wed, 11 Nov 2015 10:03:59 +0800
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On 11/10/2015 05:36 PM, Dave Young wrote:
> [snip]
>
>> diff --git a/drivers/usb/host/xhci-sysfs.c b/drivers/usb/host/xhci-sysfs.c
>> new file mode 100644
>> index 0000000..0192ac4
>> --- /dev/null
>> +++ b/drivers/usb/host/xhci-sysfs.c
>> @@ -0,0 +1,100 @@
>> +/*
>> + * sysfs interface for xHCI host controller driver
>> + *
>> + * Copyright (C) 2015 Intel Corp.
>> + *
>> + * Author: Lu Baolu <baolu.lu@linux.intel.com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + */
>> +#include <linux/kernel.h>
>> +
>> +#include "xhci.h"
>> +
>> +/*
>> + * Return the register offset of a extended capability specified
>> + * by @cap_id. Return 0 if @cap_id capability is not supported or
>> + * in error cases.
>> + */
>> +static int get_extended_capability_offset(struct xhci_hcd *xhci,
>> +					int cap_id)
>> +{
>> +	u32		cap_reg;
>> +	unsigned long	flags;
>> +	int		offset;
>> +	void __iomem	*base = (void __iomem *) xhci->cap_regs;
>> +	struct usb_hcd	*hcd = xhci_to_hcd(xhci);
>> +	int		time_to_leave = XHCI_EXT_MAX_CAPID;
>> +
>> +	spin_lock_irqsave(&xhci->lock, flags);
>> +
>> +	offset = xhci_find_next_cap_offset(base, XHCI_HCC_PARAMS_OFFSET);
>> +	if (!HCD_HW_ACCESSIBLE(hcd) || !offset) {
>> +		spin_unlock_irqrestore(&xhci->lock, flags);
>> +		return 0;
>> +	}
>> +
>> +	while (time_to_leave--) {
>> +		cap_reg = readl(base + offset);
>> +
>> +		if (XHCI_EXT_CAPS_ID(cap_reg) == cap_id)
>> +			break;
>> +
>> +		offset = xhci_find_next_cap_offset(base, offset);
>> +		if (!offset)
>> +			break;
>> +	}
>> +
>> +	spin_unlock_irqrestore(&xhci->lock, flags);
> I'm not sure spin_lock is good and necessary here, also seems there's already

The lock is unnecessary here. I will remove it.

> a function to find the cap offset:
> xhci_find_ext_cap_by_id() in xhci-ext-caps.h

Yes, I will refactor the code.

Thanks,
Baolu
>
>> +
>> +	return offset;
>> +}
>> +
> Thanks
> Dave
>

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