linux-kernel - Re: [PATCH v13 5/5] usb: xhci: provide a debugfs hook for erasing rom

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Date:   Wed, 13 May 2020 14:45:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc:     Vinod Koul <vkoul@...nel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        linux-arm-msm@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Christian Lamparter <chunkeey@...glemail.com>,
        John Stultz <john.stultz@...aro.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Andreas Böhler <dev@...ehler.at>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v13 5/5] usb: xhci: provide a debugfs hook for erasing rom

On Wed, May 13, 2020 at 03:36:19PM +0300, Mathias Nyman wrote:
> On 6.5.2020 9.00, Vinod Koul wrote:
> > run "echo 1 > /sys/kernel/debug/renesas-usb/rom_erase" to erase
> > firmware when driver is loaded.
> > 
> > Subsequent init of driver shall reload the firmware
> > 
> > Signed-off-by: Vinod Koul <vkoul@...nel.org>
> > ---
> >  drivers/usb/host/xhci-pci-renesas.c | 33 +++++++++++++++++++++++++++++
> >  1 file changed, 33 insertions(+)
> > 
> > diff --git a/drivers/usb/host/xhci-pci-renesas.c b/drivers/usb/host/xhci-pci-renesas.c
> > index f7d2445d30ec..fa32ec352dc8 100644
> > --- a/drivers/usb/host/xhci-pci-renesas.c
> > +++ b/drivers/usb/host/xhci-pci-renesas.c
> > @@ -2,6 +2,7 @@
> >  /* Copyright (C) 2019-2020 Linaro Limited */
> >  
> >  #include <linux/acpi.h>
> > +#include <linux/debugfs.h>
> >  #include <linux/firmware.h>
> >  #include <linux/module.h>
> >  #include <linux/pci.h>
> > @@ -170,6 +171,8 @@ static int renesas_fw_verify(const void *fw_data,
> >  	return 0;
> >  }
> >  
> > +static void debugfs_init(struct pci_dev *pdev);
> > +
> >  static bool renesas_check_rom(struct pci_dev *pdev)
> >  {
> >  	u16 rom_status;
> > @@ -183,6 +186,7 @@ static bool renesas_check_rom(struct pci_dev *pdev)
> >  	rom_status &= RENESAS_ROM_STATUS_ROM_EXISTS;
> >  	if (rom_status) {
> >  		dev_dbg(&pdev->dev, "External ROM exists\n");
> > +		debugfs_init(pdev);
> >  		return true; /* External ROM exists */
> >  	}
> >  
> > @@ -449,6 +453,34 @@ static void renesas_rom_erase(struct pci_dev *pdev)
> >  	dev_dbg(&pdev->dev, "ROM Erase... Done success\n");
> >  }
> >  
> > +static int debugfs_rom_erase(void *data, u64 value)
> > +{
> > +	struct pci_dev *pdev = data;
> > +
> > +	if (value == 1) {
> > +		dev_dbg(&pdev->dev, "Userspace requested ROM erase\n");
> > +		renesas_rom_erase(pdev);
> > +		return 0;
> > +	}
> > +	return -EINVAL;
> > +}
> > +DEFINE_DEBUGFS_ATTRIBUTE(rom_erase_ops, NULL, debugfs_rom_erase, "%llu\n");
> > +
> > +static struct dentry *debugfs_root;
> > +
> > +static void debugfs_init(struct pci_dev *pdev)
> > +{
> > +	debugfs_root = debugfs_create_dir("renesas_usb", NULL);
> 
> This will create a renesas_usb directory right under debugfs root.
> xhci has its own struct dentry xhci_debugfs_root; 
> Use that as parent instead

Ah, I misssed that, a follow-on patch can do this, right?

> Also note that debugs_create_dir() can fail, for example if debugfs isn't supported.    

Doesn't matter, never check the result, just move on and all is fine :)

This logic is correct, no need for it to be changed.

thanks,

greg k-h