linux-kernel - Re: sound/pci/ctxfi/ctdaio.c: duplicate function removal question

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Message-ID: <87bjwuy9ub.wl-tiwai@suse.de>
Date: Sun, 29 Dec 2024 13:03:56 +0100
From: Takashi Iwai <tiwai@...e.de>
To: David Laight <david.laight.linux@...il.com>
Cc: Takashi Iwai <tiwai@...e.de>,
	Ethan Carter Edwards <ethan@...ancedwards.com>,
	"wychay@....creative.com" <wychay@....creative.com>,
	"ryan_richards@...ativelabs.com" <ryan_richards@...ativelabs.com>,
	"linux-sound@...r.kernel.org" <linux-sound@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: sound/pci/ctxfi/ctdaio.c: duplicate function removal question

On Sun, 29 Dec 2024 11:57:22 +0100,
David Laight wrote:
> 
> On Sun, 29 Dec 2024 10:10:09 +0100
> Takashi Iwai <tiwai@...e.de> wrote:
> 
> > On Sun, 29 Dec 2024 10:02:28 +0100,
> > David Laight wrote:
> > > 
> > > On Tue, 24 Dec 2024 23:16:17 +0000
> > > Ethan Carter Edwards <ethan@...ancedwards.com> wrote:
> > >   
> > > > Hello all,
> > > > 
> > > > First of all, happy holidays. 
> > > > 
> > > > I was browsing the ctdaio.c code and I noticed a lot of 
> > > > duplicate code and functions, specifically:
> > > > 
> > > > dao_set_{right,left}_input and
> > > > dao_clear_{right,left}_input functions.
> > > > 
> > > > The functions are pretty much identical. They only 
> > > > differ in the side (left, right). What was the original
> > > > idea in doing this? Wouldn't it make more since to just
> > > > have an ENUM (left, right) as an argument that would 
> > > > determine the side and just reduce the function to 
> > > > dao_set_input and dao_clear_input.  
> > > 
> > > Hmmm... you'd have a lot of conditionals inside the function.
> > > 
> > > They also look like a memory leak just waiting to happen.
> > > I guess that an earlier implementation used a separate kmalloc()
> > > for each imappers[].
> > > 
> > > Why is imappers[] an array of pointers not an array of the items?
> > > Each is just 8 bytes plus a 'list_head' (2 pointers?).  
> > 
> > AFAIUC, it's a setup of a chained element, so no leak there as of
> > now.
> 
> Unless someone calls the functions in the wrong order.
> And that seems to be outside the control of this code.

Could you elaborate?  The chain element gets released also by the
destructor, dao_rsc_uninit().  And this is no exported function to be
used by other drivers, but an internal one only for ctxfi driver.


thanks,

Takashi