From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752627AbeAFToD (ORCPT + 1 other); Sat, 6 Jan 2018 14:44:03 -0500 Received: from mail-wm0-f67.google.com ([74.125.82.67]:38755 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751509AbeAFToC (ORCPT ); Sat, 6 Jan 2018 14:44:02 -0500 X-Google-Smtp-Source: ACJfBouUo0ftaDXwoC/817t4GwtkDfBG09W/3Nvgt1Be9ZphVcRfPEy87fTKLopbwvZPNGiLKFbYFQ== Subject: Re: [PATCH] vboxvideo: Fix incorrect type in assignment sparse warning To: Alexander Kapshuk Cc: Greg KH , michael.thayer@oracle.com, dri-devel@lists.freedesktop.org, peda@axentia.se, Daniel Vetter , =?UTF-8?Q?Cihangir_Akt=c3=bcrk?= , Sean Paul , linux-kernel References: From: Hans de Goede Message-ID: <6f4de025-b126-9819-d789-ef611c9f82d9@redhat.com> Date: Sat, 6 Jan 2018 20:43:59 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: HI, On 06-01-18 20:30, Alexander Kapshuk wrote: > On Sat, Jan 6, 2018 at 6:00 PM, Hans de Goede wrote: >> Hi, >> >> >> On 06-01-18 15:20, Alexander Kapshuk wrote: >>> >>> On Mon, Dec 25, 2017 at 04:42:59PM +0200, Alexander Kapshuk wrote: >>>> >>>> Sparse emitted the following warning: >>>> ../drivers/staging/vboxvideo/vbox_fb.c:173:27: warning: incorrect type in >>>> assignment (different address spaces) >>>> ../drivers/staging/vboxvideo/vbox_fb.c:173:27: expected char [noderef] >>>> *screen_base >>>> ../drivers/staging/vboxvideo/vbox_fb.c:173:27: got void *virtual >>>> >>>> The vbox_bo buffer object kernel mapping is handled by a call >>>> to ttm_bo_kmap() prior to the assignment of bo->kmap.virtual to >>>> info->screen_base of type char __iomem*. >>>> Casting bo->kmap.virtual to char __iomem* in this assignment fixes >>>> the warning. >>>> >>>> vboxvideo: Fix address space of expression removal sparse warning >>>> >>>> Sparse emitted the following warning: >>>> ../drivers/staging/vboxvideo/vbox_main.c:64:25: warning: cast removes >>>> address space of expression >>>> >>>> vbox->vbva_buffers iomapping is handled by calling vbox_accel_init() >>>> from vbox_hw_init(). >>>> __force attribute is used in assignment to vbva to fix the warning. >>>> >>>> Signed-off-by: Alexander Kapshuk >>>> --- >>>> drivers/staging/vboxvideo/vbox_fb.c | 2 +- >>>> drivers/staging/vboxvideo/vbox_main.c | 2 +- >>>> 2 files changed, 2 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/staging/vboxvideo/vbox_fb.c >>>> b/drivers/staging/vboxvideo/vbox_fb.c >>>> index 8aed248db6e2..43c39eca4ae1 100644 >>>> --- a/drivers/staging/vboxvideo/vbox_fb.c >>>> +++ b/drivers/staging/vboxvideo/vbox_fb.c >>>> @@ -170,7 +170,7 @@ static int vboxfb_create(struct drm_fb_helper >>>> *helper, >>>> drm_fb_helper_fill_var(info, &fbdev->helper, sizes->fb_width, >>>> sizes->fb_height); >>>> >>>> - info->screen_base = bo->kmap.virtual; >>>> + info->screen_base = (char __iomem *)bo->kmap.virtual; >>>> info->screen_size = size; >>>> >>>> #ifdef CONFIG_DRM_KMS_FB_HELPER >> >> >> This fix looks good to me. >> >>>> diff --git a/drivers/staging/vboxvideo/vbox_main.c >>>> b/drivers/staging/vboxvideo/vbox_main.c >>>> index 80bd039fa08e..973b3bcc04b1 100644 >>>> --- a/drivers/staging/vboxvideo/vbox_main.c >>>> +++ b/drivers/staging/vboxvideo/vbox_main.c >>>> @@ -61,7 +61,7 @@ void vbox_enable_accel(struct vbox_private *vbox) >>>> if (vbox->vbva_info[i].vbva) >>>> continue; >>>> >>>> - vbva = (void *)vbox->vbva_buffers + i * >>>> VBVA_MIN_BUFFER_SIZE; >>>> + vbva = (void __force *)vbox->vbva_buffers + i * >>>> VBVA_MIN_BUFFER_SIZE; >>>> if (!vbva_enable(&vbox->vbva_info[i], >>>> vbox->guest_pool, vbva, i)) { >>>> /* very old host or driver error. */ >> >> >> Hmm, isn't there a cleaner way to fix this ? Maybe make vbva_enable's >> argument (and the local vbva variable) of type u8 __iomem * too ? >> >> Regards, >> >> Hans > > Hi Hans, > > Thanks for your prompt response. > > I had a good look at the vbva_enable() function's definition and to > the best of my knowledge, changing vbva's type from 'struct > vbva_buffer *' to 'u8 __iomem *' wouldn't work. > vbva_enable() relies on vbva's type being a pointer to 'struct vbva_buffer': > vbva's memory gets set to zero; > some of vbva's members are initialised to particular values; > vbva_ctx->vbva expects vbva to be a pointer to 'struct vbva_buffer' as well; > > Or am I misreading this? No your not misreading this I did not check the function myself before commenting myself, my bad. > What are your thoughts on this? Lets just move ahead with your original fix: Reviewed-by: Hans de Goede Regards, Hans