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[82.37.195.13]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-466648c5de7sm35009927f8f.15.2026.06.23.06.17.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Jun 2026 06:17:55 -0700 (PDT) Date: Tue, 23 Jun 2026 14:17:54 +0100 From: Daniel Thompson To: "Sverdlin, Alexander" Cc: "dri-devel@lists.freedesktop.org" , "danielt@kernel.org" , "linux-leds@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-fbdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 3/3] backlight: lp8864: Convert from LED to backlight class driver Message-ID: References: <20260615120353.3409035-1-alexander.sverdlin@siemens.com> <20260615120353.3409035-4-alexander.sverdlin@siemens.com> <0b39450b-559b-43d4-a1e9-bb6684691cb5@ti.com> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Jun 23, 2026 at 11:59:16AM +0000, Sverdlin, Alexander wrote: > Hi Daniel, > > On Tue, 2026-06-23 at 12:41 +0100, Daniel Thompson wrote: > > > The mechanism we have regarding hot plugging currently is just I2C bridge, > > > which de-registers and registers the bridged bus. So no additional drivers > > > are required, as long as I2C devices are self-contained and not glued with > > > platform devices. > > > > > > So bottom line is, I'd prefer to just add the backlight interface to the > > > existing driver, no matter where it would live in the future. > > > > Is there any reasion that LP8864/LP8866 is unique in appearing on a > > hotplugged I2C bus? In other words if support for dynamism is added > > specifically to leds-lp8864.c rather than in led_bl.c then what will stop > > the same dynamic tricks from being adde to other LED drivers? > > LP8864 is not special in this regard, not different from adp8860_bl.c, > adp8870_bl.c or lm3639_bl.c, which would work in my application. The most recent of these drivers adopted LED support in 2012 whilst led_bl.c was introduced in 2020. > So I just wanted to add currently missing backlight_device_register() to > LP8864, but there were no such dual-API drivers under drivers/leds/ that's > wht I started with moving LP8864 driver into drivers/video/backlight/. > > led_bl.c however could only be hot-pluggable either if one actively > creates/destroys platform device somewhere in the code programmatically > or uses DT overlays. > > Just adding backlight API to LP8864 would be much more idiomatic, I'd > say. Maybe. I think I might consider the drivers above to be historical anomalies rather than idiomatic examples. Daniel.