linux-kernel - Re: [PATCH v9 4/4] drm/panthor: show device-wide list of DRM GEM objects over DebugFS

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Message-ID: <20250418102649.41a609d6@collabora.com>
Date: Fri, 18 Apr 2025 10:26:49 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>
Cc: linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 kernel@...labora.com, Liviu Dudau <liviu.dudau@....com>, Steven Price
 <steven.price@....com>, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Sumit Semwal <sumit.semwal@...aro.org>,
 Christian König <christian.koenig@....com>,
 linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v9 4/4] drm/panthor: show device-wide list of DRM GEM
 objects over DebugFS

On Fri, 18 Apr 2025 10:11:56 +0200
Boris Brezillon <boris.brezillon@...labora.com> wrote:

> On Fri, 18 Apr 2025 03:27:07 +0100
> Adrián Larumbe <adrian.larumbe@...labora.com> wrote:
> 
> > +	static const char * const gem_state_flags_names[] = {
> > +		[PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED] = "imported",

FYI, the compiler seems to be happy with:

		[ffs(PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED) - 1] = "imported",

but I'm not sure we want to fix it this way. The other
option would be to define bit pos in the enum and then
define flags according to these bit pos:

enum panthor_debugfs_gem_state_flags {
	PANTHOR_DEBUGFS_GEM_STATE_IMPORTED_BIT = 0,
	PANTHOR_DEBUGFS_GEM_STATE_EXPORTED_BIT = 1,

	/** @PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED: GEM BO is PRIME imported. */
	PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED = BIT(PANTHOR_DEBUGFS_GEM_STATE_IMPORTED_BIT),

	/** @PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED: GEM BO is PRIME exported. */
	PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED = BIT(PANTHOR_DEBUGFS_GEM_STATE_EXPORTED_BIT),
};

> > +		[PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED] = "exported",  
> 
> Okay, I think I know where the flag indexing issue comes from:
> PANTHOR_DEBUGFS_GEM_STATE_FLAG_xx are flags, not bit positions, so we
> can't use them as indices here.
> 
> > +	};
> > +
> > +	static const char * const gem_usage_flags_names[] = {
> > +		[PANTHOR_DEBUGFS_GEM_USAGE_FLAG_KERNEL] = "kernel",
> > +		[PANTHOR_DEBUGFS_GEM_USAGE_FLAG_FW_MAPPED] = "fw-mapped",  
> 
> Same problem here.
> 
> > +	};
> > +