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Date:   Tue, 3 Nov 2020 08:15:35 -0800
From:   Jakub Kicinski <kuba@kernel.org>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Hayes Wang <hayeswang@realtek.com>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        nic_swsd <nic_swsd@realtek.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        Oliver Neukum <oliver@neukum.org>
Subject: Re: [PATCH net-next v2] net/usb/r8153_ecm: support ECM mode for
 RTL8153
Message-ID: <20201103081535.7e92a495@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
In-Reply-To: <20201103093241.GA79239@kroah.com>
References: <1394712342-15778-387-Taiwan-albertk@realtek.com>
        <1394712342-15778-388-Taiwan-albertk@realtek.com>
        <20201031160838.39586608@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
        <dc7fd1d4d1c544e8898224c7d9b54bda@realtek.com>
        <20201102114718.0118cc12@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
        <20201103093241.GA79239@kroah.com>
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On Tue, 3 Nov 2020 10:32:41 +0100 Greg Kroah-Hartman wrote:
> On Mon, Nov 02, 2020 at 11:47:18AM -0800, Jakub Kicinski wrote:
> > On Mon, 2 Nov 2020 07:20:15 +0000 Hayes Wang wrote:  
> > > Jakub Kicinski <kuba@kernel.org>  
> > > > Can you describe the use case in more detail?
> > > > 
> > > > AFAICT r8152 defines a match for the exact same device.
> > > > Does it not mean that which driver is used will be somewhat random
> > > > if both are built?    
> > > 
> > > I export rtl_get_version() from r8152. It would return none zero
> > > value if r8152 could support this device. Both r8152 and r8153_ecm
> > > would check the return value of rtl_get_version() in porbe().
> > > Therefore, if rtl_get_version() return none zero value, the r8152
> > > is used for the device with vendor mode. Otherwise, the r8153_ecm
> > > is used for the device with ECM mode.  
> > 
> > Oh, I see, I missed that the rtl_get_version() checking is the inverse
> > of r8152.
> >   
> > > > > +/* Define these values to match your device */
> > > > > +#define VENDOR_ID_REALTEK		0x0bda
> > > > > +#define VENDOR_ID_MICROSOFT		0x045e
> > > > > +#define VENDOR_ID_SAMSUNG		0x04e8
> > > > > +#define VENDOR_ID_LENOVO		0x17ef
> > > > > +#define VENDOR_ID_LINKSYS		0x13b1
> > > > > +#define VENDOR_ID_NVIDIA		0x0955
> > > > > +#define VENDOR_ID_TPLINK		0x2357    
> > > > 
> > > > $ git grep 0x2357 | grep -i tplink
> > > > drivers/net/usb/cdc_ether.c:#define TPLINK_VENDOR_ID	0x2357
> > > > drivers/net/usb/r8152.c:#define VENDOR_ID_TPLINK		0x2357
> > > > drivers/usb/serial/option.c:#define TPLINK_VENDOR_ID			0x2357
> > > > 
> > > > $ git grep 0x17ef | grep -i lenovo
> > > > drivers/hid/hid-ids.h:#define USB_VENDOR_ID_LENOVO		0x17ef
> > > > drivers/hid/wacom.h:#define USB_VENDOR_ID_LENOVO	0x17ef
> > > > drivers/net/usb/cdc_ether.c:#define LENOVO_VENDOR_ID	0x17ef
> > > > drivers/net/usb/r8152.c:#define VENDOR_ID_LENOVO		0x17ef
> > > > 
> > > > Time to consolidate those vendor id defines perhaps?    
> > > 
> > > It seems that there is no such header file which I could include
> > > or add the new vendor IDs.  
> > 
> > Please create one. (Adding Greg KH to the recipients, in case there is
> > a reason that USB subsystem doesn't have a common vendor id header.)  
> 
> There is a reason, it's a nightmare to maintain and handle merges for,
> just don't do it.

Ah! Good that we asked :)

> Read the comments at the top of the pci_ids.h file if you are curious
> why we don't even do this for PCI device ids anymore for the past 10+
> years.
> 
> So no, please do not create such a common file, it is not needed or a
> good idea.

I wouldn't go that far, PCI subsystem just doesn't want everyone to add
IDs to the shared file unless there is a reason.

 *	Do not add new entries to this file unless the definitions
 *	are shared between multiple drivers.

Which seems quite reasonable. But it is most certainly your call :)