linux-kernel - Re: [PATCH v5] Bluetooth: NXP: Add protocol support for NXP Bluetooth chipsets

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Date:   Thu, 23 Feb 2023 14:06:01 +0000
From:   Neeraj sanjay kale <neeraj.sanjaykale@....com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "marcel@...tmann.org" <marcel@...tmann.org>,
        "johan.hedberg@...il.com" <johan.hedberg@...il.com>,
        "luiz.dentz@...il.com" <luiz.dentz@...il.com>,
        "jirislaby@...nel.org" <jirislaby@...nel.org>,
        "alok.a.tiwari@...cle.com" <alok.a.tiwari@...cle.com>,
        "hdanton@...a.com" <hdanton@...a.com>,
        "ilpo.jarvinen@...ux.intel.com" <ilpo.jarvinen@...ux.intel.com>,
        "leon@...nel.org" <leon@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        Amitkumar Karwar <amitkumar.karwar@....com>,
        Rohit Fule <rohit.fule@....com>,
        Sherry Sun <sherry.sun@....com>
Subject: Re: [PATCH v5] Bluetooth: NXP: Add protocol support for NXP Bluetooth
 chipsets


Hi Greg,

Thank you again for the feedback.
I will work on this and submit a new patch again.

Thanks,
Neeraj

> 
> On Thu, Feb 23, 2023 at 01:57:58PM +0000, Neeraj sanjay kale wrote:
> > Hi Greg,
> >
> > Thank you for your feedback.
> >
> > >
> > > > +
> > > > +static int init_baudrate = 115200;
> > >
> > > and neither will this, as you need to support multiple devices in
> > > the system, your driver should never be only able to work with one
> device.
> > > Please make these device-specific things, not the same for the whole
> driver.
> > >
> >
> > I am using this init_baudrate as a module parameter static int
> > init_baudrate = 115200; module_param(init_baudrate, int, 0444);
> > MODULE_PARM_DESC(init_baudrate, "host baudrate after FW download:
> > default=115200");
> 
> Ah, totally missed that.
> 
> That is not ok, sorry, this is not the 1990's, we do not use module parameters
> for drivers as that obviously does not work at all for when you have multiple
> devices controlled by that driver.  Please make this all dynamic and "just
> work" properly for all devices.
> 
> > We need this parameter configurable since different chip module vendors
> using the same NXP chipset, configure these chips differently.
> 
> Then you are pushing the configuration to userspace for someone else to put
> on their boot command line?  that's crazy, please never do that.
> 
> > For example, module vendor A distributes his modules based on NXP
> 88w8987 chips with a different configuration compared to module vendor B
> (based on NXP 88w8987), and the init_baudrate is one of the important
> distinctions between them.
> 
> Then put that logic in DT where it belongs.
> 
> > If we are able to keep this init_baudrate configurable, while compiling
> btnxpuart.ko as module, we will be able to support such baudrate variations.
> 
> Again, no, that's not how tty or serial devices work.
> 
> thanks,
> 
> greg k-h