From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f50.google.com (mail-wm1-f50.google.com [209.85.128.50]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9A13230C17D for ; Tue, 23 Jun 2026 13:18:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.50 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782220684; cv=none; b=pZaxR6ruyZxkkioMJoONQc/lGI9VVvNyC2WjOPNEPgGz6yp5LvCzYQZaJ6jBIaPQD0ASTGXeqJu7p38s0bsiIDkObzsiNIV8umObj5ah/8XAUdxyng9Y3gwZDCm6FcldCQfg1E+NRM51xZuanDtxFFg32FJB38Law5uJvVdhAUE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782220684; c=relaxed/simple; bh=QWksKsu3aFjbz0U7IDFysKky5YyDvWjjH+s0LaexQxM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=iWl7kJPq//4CffZJk32P09DuhmEyvbYjRUpaZP6tPyUNhPj9dhBp0pfJ7uiBCPlsA8iJD3KEVfICQIbXBe/5aLBLmHLEq1MQTZUEGDuaPRFEoRt/aYTNQ500utgYQPJA/4l4oAxaetDurRwY7f6rbRVVvVyo+L1HWaYfS/HvTBM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=riscstar.com; spf=pass smtp.mailfrom=riscstar.com; dkim=pass (2048-bit key) header.d=riscstar-com.20251104.gappssmtp.com header.i=@riscstar-com.20251104.gappssmtp.com header.b=LRUJmFDC; arc=none smtp.client-ip=209.85.128.50 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=riscstar.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=riscstar.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=riscstar-com.20251104.gappssmtp.com header.i=@riscstar-com.20251104.gappssmtp.com header.b="LRUJmFDC" Received: by mail-wm1-f50.google.com with SMTP id 5b1f17b1804b1-490b7866869so55629095e9.2 for ; Tue, 23 Jun 2026 06:18:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=riscstar-com.20251104.gappssmtp.com; s=20251104; t=1782220681; x=1782825481; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=xQjsOKmDv4bAeAAg8kHxPjywYyxr88XeXI1w7+vf02M=; b=LRUJmFDCPthifYRMfZhYIydgCNTbxhaAg+fwOLgzNj8ZVf8RkBIVX6dwaigUKzLs++ 1QbcBRqkV6/V5rIROWULa/4il6+DXssu0ODMgHHxZMNf9qSxLPLDLdR0HqRcRyHijn5r HjbhBzlT7dxKEPFLAqxzPbrYk/9EFXZ9fmY4XAf4Jq4rBMV8TZxZkYhfvWc7i4tPFGqB E51EArs9o1X93L7IHgMYpK0iV3UJ7ynnwbt7fLycxsZAIXHHA3CP5rZijioxBkz39JGX xgeKE+PjZ6dNBp1W4rcM/smOx5In9Y8SlpocKbsM+D8vXUrZH9aYxKitHWQcCfhHvJ8b I+OQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782220681; x=1782825481; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=xQjsOKmDv4bAeAAg8kHxPjywYyxr88XeXI1w7+vf02M=; b=BUBDoPQ90L8wUGrllq1LjnpdHaA6SibZXTxaUhcXZN94E+bUOXKf5XmihaoI9M5EvR 2Oum9gkfRJ/V8XWCwmqVR/N9p7fx4vj8m9x8SGp9RaFd2jQnUsqfkMfSqNAagKHhcA/Y qC6glWGhQfVhysxmhpfdLvpG5GEl8bFvQic28Fji4N+1qt9mDKBB2n+pKF47ls2i8UYl rTqV7P8I7XWGEJ8ANmeYWhNTBx8dedhxYLhMv2dl0urcX4IOR/Fig1ZhpTgPyuCjnibT yxZcR/IeUgD4tfy7hjS0j+akenBrs85E5laHWHZfGjTjgEwC7P5K4bpo5M9CQ510m4mU e8Kg== X-Forwarded-Encrypted: i=1; AFNElJ+PogdTJ1kvxkKvrOGVhsQDin3GuZb5PloRaV9lJr3uxI3PLKOH1hOa0+SIPKNtaGfr1eXuRNdKQmmK5Q==@vger.kernel.org X-Gm-Message-State: AOJu0Yz4B4wO8XRQvOewIAAApPXPCVjVgmeeJXMSforHoNKKJLk6wHLV eaafJdHgR1MuvEM9EZoMDxteIjwkJjFO5xo+dqPnK+OzKgz6PaypOpim79oZkrbIivE= X-Gm-Gg: AfdE7clgsK7S3X+FGm7owabOdt6+EhiOLkqC3Wa/6s1tg5tgNN6QynvHaXVe1cijqeG iGmlJwhlvI3wgWtsRUQYOww9ZVzc3whtxyRd1Crpod5hh7lHcHjspV152m5iwOWG48M/sRaJMrX eAdYKPACj+yxJP4boq/iGxuJ7OOrx6i76K0oha6jNG3o4cVCngqKHaS5Q8yR4Xs5mzjTukHtl4H skySt/DBm+yYoDzoE9pzRlDk4VPws0orKz/uyFk9Yq9r3mGLdHICEQczZCiPMHoZm+D+vibNhH6 oXGrWITNZ31hg07009WipS/3VkWRbxkdqJmpX1Qel1SCLfqZYpbLWfWUeW4EKZpsRfV3lGa6e4E Nb0wk0nlERNIYWR+1qhkrcDYBNdZGZFmU2FHodm6i/sb1X5ZEqdgz0f7cc+KoZyaNoMIxNqOAiE I2OgHhpHU79EvOsIWSn41cqjX9VLPfeQpEMRg8yVhCNKD2Zv0buQJMJmIHeEJZQF0RxYsDkrUga eLu+Y8aEuCnq8WCLhZisGsUqYlkN6HlkJHrXX/Q8HD6Q3j14sdRCkpHHfXU7rnxW5w3giL21w== X-Received: by 2002:a05:600c:1548:b0:492:39b6:5a30 with SMTP id 5b1f17b1804b1-4925b38f01bmr37906055e9.35.1782220676494; Tue, 23 Jun 2026 06:17:56 -0700 (PDT) Received: from aspen.lan (aztw-34-b2-v4wan-166919-cust780.vm26.cable.virginm.net. [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: linux-fbdev@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.