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Date:   Thu, 7 Jul 2022 18:12:26 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Marek =?iso-8859-1?Q?Beh=FAn?= <kabel@kernel.org>
Cc:     linux-serial@vger.kernel.org,
        Pali =?iso-8859-1?Q?Roh=E1r?= <pali@kernel.org>
Subject: Re: [PATCH 5/7] USB: serial: ftdi_sio: Fix baudrate rounding for
 ASYNC_SPD_CUST
Message-ID: <YscF6pONFktLx3el@kroah.com>
References: <20220707145354.29705-1-kabel@kernel.org>
 <20220707145354.29705-6-kabel@kernel.org>
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On Thu, Jul 07, 2022 at 06:08:18PM +0200, Marek Behún wrote:
> On Thu, 7 Jul 2022 17:11:00 +0200
> Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> 
> > On Thu, Jul 07, 2022 at 04:53:52PM +0200, Marek Behún wrote:
> > > From: Pali Rohár <pali@kernel.org>
> > > 
> > > Use DIV_ROUND_CLOSEST() for more accurate baudrate calculation for
> > > ASYNC_SPD_CUST instead of rounding it just down.  
> > 
> > Why?  What does this change or fix?
> 
> To compute more accurate baudrate when given custom divisor.
> 
> User requests a baudrate B.
> Application uses old API, so it computes divisor D for baudrate B.
> The driver then tries to compute back the requested baudrate B. To
> compute it back more accurately, rounding to closes value should be
> used.

Then please describe this in the changelog text, don't make us guess...