| Message ID | 20190313010428.116678-1-tutankhamen@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/udl: Refactor edid retreiving in UDL driver | expand |
On Tue, 12 Mar 2019, Robert Tarasov <tutankhamen@chromium.org> wrote: > Now drm/udl driver uses drm_do_get_edid() function to retreive and > validate all blocks of EDID data. Old approach had insufficient > validation routine and had problems with retreiving of extra blocks You'll also get support for debugfs and firmware loader EDID override mechanisms for free. Fixes: 75c65ee20ade ("drm/udl: Reading all edid blocks in DRM/UDL driver") Signed-off-by missing! > --- > drivers/gpu/drm/udl/udl_connector.c | 72 +++++------------------------ > 1 file changed, 11 insertions(+), 61 deletions(-) > > diff --git a/drivers/gpu/drm/udl/udl_connector.c b/drivers/gpu/drm/udl/udl_connector.c > index c3dc1fd20cb4..c7f8ac2cdbe5 100644 > --- a/drivers/gpu/drm/udl/udl_connector.c > +++ b/drivers/gpu/drm/udl/udl_connector.c > @@ -17,18 +17,19 @@ > #include "udl_connector.h" > #include "udl_drv.h" > > -static bool udl_get_edid_block(struct udl_device *udl, int block_idx, > - u8 *buff) > +static int udl_get_edid_block(void *data, u8 *buf, unsigned int block, > + size_t len) > { > int ret, i; > u8 *read_buff; > + struct udl_device *udl = data; > > read_buff = kmalloc(2, GFP_KERNEL); A follow-up cleanup might be to switch to using "u8 read_buff[2];" instead of kmallocing it. I don't claim to understand how the usb stuff works, but otherwise the patch looks good to me. Nice refactoring! Reviewed-by: Jani Nikula <jani.nikula@intel.com> > if (!read_buff) > - return false; > + return -1; > > - for (i = 0; i < EDID_LENGTH; i++) { > - int bval = (i + block_idx * EDID_LENGTH) << 8; > + for (i = 0; i < len; i++) { > + int bval = (i + block * EDID_LENGTH) << 8; > ret = usb_control_msg(udl->udev, > usb_rcvctrlpipe(udl->udev, 0), > (0x02), (0x80 | (0x02 << 5)), bval, > @@ -36,60 +37,13 @@ static bool udl_get_edid_block(struct udl_device *udl, int block_idx, > if (ret < 1) { > DRM_ERROR("Read EDID byte %d failed err %x\n", i, ret); > kfree(read_buff); > - return false; > + return -1; > } > - buff[i] = read_buff[1]; > + buf[i] = read_buff[1]; > } > > kfree(read_buff); > - return true; > -} > - > -static bool udl_get_edid(struct udl_device *udl, u8 **result_buff, > - int *result_buff_size) > -{ > - int i, extensions; > - u8 *block_buff = NULL, *buff_ptr; > - > - block_buff = kmalloc(EDID_LENGTH, GFP_KERNEL); > - if (block_buff == NULL) > - return false; > - > - if (udl_get_edid_block(udl, 0, block_buff) && > - memchr_inv(block_buff, 0, EDID_LENGTH)) { > - extensions = ((struct edid *)block_buff)->extensions; > - if (extensions > 0) { > - /* we have to read all extensions one by one */ > - *result_buff_size = EDID_LENGTH * (extensions + 1); > - *result_buff = kmalloc(*result_buff_size, GFP_KERNEL); > - buff_ptr = *result_buff; > - if (buff_ptr == NULL) { > - kfree(block_buff); > - return false; > - } > - memcpy(buff_ptr, block_buff, EDID_LENGTH); > - kfree(block_buff); > - buff_ptr += EDID_LENGTH; > - for (i = 1; i < extensions; ++i) { > - if (udl_get_edid_block(udl, i, buff_ptr)) { > - buff_ptr += EDID_LENGTH; > - } else { > - kfree(*result_buff); > - *result_buff = NULL; > - return false; > - } > - } > - return true; > - } > - /* we have only base edid block */ > - *result_buff = block_buff; > - *result_buff_size = EDID_LENGTH; > - return true; > - } > - > - kfree(block_buff); > - > - return false; > + return 0; > } > > static int udl_get_modes(struct drm_connector *connector) > @@ -121,8 +75,6 @@ static int udl_mode_valid(struct drm_connector *connector, > static enum drm_connector_status > udl_detect(struct drm_connector *connector, bool force) > { > - u8 *edid_buff = NULL; > - int edid_buff_size = 0; > struct udl_device *udl = connector->dev->dev_private; > struct udl_drm_connector *udl_connector = > container_of(connector, > @@ -135,12 +87,10 @@ udl_detect(struct drm_connector *connector, bool force) > udl_connector->edid = NULL; > } > > - > - if (!udl_get_edid(udl, &edid_buff, &edid_buff_size)) > + udl_connector->edid = drm_do_get_edid(connector, udl_get_edid_block, udl); > + if (!udl_connector->edid) > return connector_status_disconnected; > > - udl_connector->edid = (struct edid *)edid_buff; > - > return connector_status_connected; > }
On Wed, Mar 13, 2019 at 2:26 AM Jani Nikula <jani.nikula@linux.intel.com> wrote: > You'll also get support for debugfs and firmware loader EDID override > mechanisms for free. > Yep :) > Signed-off-by missing! > Fixed. read_buff = kmalloc(2, GFP_KERNEL); > > A follow-up cleanup might be to switch to using "u8 read_buff[2];" > instead of kmallocing it. > > I don't claim to understand how the usb stuff works, but otherwise the > patch looks good to me. Nice refactoring! > > "The buffer passed to usb_control_msg may end up in scatter-gather list, and may thus not be on the stack. Having it on the stack usually works on x86, but not on other archs. " <div dir="ltr"><div dir="ltr"><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Mar 13, 2019 at 2:26 AM Jani Nikula <<a href="mailto:jani.nikula@linux.intel.com">jani.nikula@linux.intel.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">You'll also get support for debugfs and firmware loader EDID override<br> mechanisms for free.<br></blockquote><div><br></div><div>Yep :) </div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Signed-off-by missing!<br></blockquote><div><br></div><div>Fixed.</div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> read_buff = kmalloc(2, GFP_KERNEL);<br> <br> A follow-up cleanup might be to switch to using "u8 read_buff[2];"<br> instead of kmallocing it.<br> <br> I don't claim to understand how the usb stuff works, but otherwise the<br> patch looks good to me. Nice refactoring!<br><br></blockquote><div><br></div><span style="font-size:13px">"The buffer passed to usb_control_msg may end up in scatter-gather list, and </span><span style="font-size:13px">may thus not be on the stack. Having it on the stack usually works on x86, </span><span style="font-size:13px">but </span><span style="font-size:13px">not on other archs.</span><span style="font-size:13px"> "</span></div></div>
On Wed, 13 Mar 2019, Robert Tarasov <tutankhamen@chromium.org> wrote: > On Wed, Mar 13, 2019 at 2:26 AM Jani Nikula <jani.nikula@linux.intel.com> > wrote: > read_buff = kmalloc(2, GFP_KERNEL); >> >> A follow-up cleanup might be to switch to using "u8 read_buff[2];" >> instead of kmallocing it. >> >> I don't claim to understand how the usb stuff works, but otherwise the >> patch looks good to me. Nice refactoring! >> >> > "The buffer passed to usb_control_msg may end up in scatter-gather list, > and may thus not be on the stack. Having it on the stack usually works on > x86, but not on other archs. " Apparently you're referring to commit 242187b36255 ("udldrmfb: udl_get_edid: usb_control_msg buffer must not be on the stack"). Cc: Hans. Mind blows. Not a word on this anywhere in usb_control_msg() documentation. Nothing. I found this patch [1] that never go applied, which doesn't actually say anything about stack, only alignment and padding. Cc: Mauro. I think with this usb_control_msg() goes to negative levels in Rusty's API design manifesto. BR, Jani. [1] http://mid.mail-archive.com/ee3ea6944e095fa3b2383697a967f4bc9e2d9631.1490813422.git.mchehab@s-opensource.com
Hi, On 14-03-19 11:00, Jani Nikula wrote: > On Wed, 13 Mar 2019, Robert Tarasov <tutankhamen@chromium.org> wrote: >> On Wed, Mar 13, 2019 at 2:26 AM Jani Nikula <jani.nikula@linux.intel.com> >> wrote: >> read_buff = kmalloc(2, GFP_KERNEL); >>> >>> A follow-up cleanup might be to switch to using "u8 read_buff[2];" >>> instead of kmallocing it. >>> >>> I don't claim to understand how the usb stuff works, but otherwise the >>> patch looks good to me. Nice refactoring! >>> >>> >> "The buffer passed to usb_control_msg may end up in scatter-gather list, >> and may thus not be on the stack. Having it on the stack usually works on >> x86, but not on other archs. " > > Apparently you're referring to commit 242187b36255 ("udldrmfb: > udl_get_edid: usb_control_msg buffer must not be on the stack"). Cc: > Hans. Right, that is correct, note this is enforced by the usb-core, having the buffer on the stack will trigger a WARN_ONCE in drivers/usb/core/hcd.c: usb_hcd_map_urb_for_dma() even on x86. > Mind blows. Not a word on this anywhere in usb_control_msg() > documentation. Nothing. I found this patch [1] that never go applied, > which doesn't actually say anything about stack, only alignment and > padding. Cc: Mauro. I guess this is something everyone who works regularly on USB drivers just learned once the hard way by triggering (and then fixing) the WARN_ONCE. Note I'm not trying to make an excuse for the lacking docs here, just trying to provide some background. I fully agree that the docs should be updated to say that the buffer must be dma-able and thus must not be on the stack. Maybe the docs should simply say something along the lines of: "the buffer should be dma-capable and properly aligned for dma, it is advisable to use a dedictated kmalloc-ed buffer for this" Regards, Hans
diff --git a/drivers/gpu/drm/udl/udl_connector.c b/drivers/gpu/drm/udl/udl_connector.c index c3dc1fd20cb4..c7f8ac2cdbe5 100644 --- a/drivers/gpu/drm/udl/udl_connector.c +++ b/drivers/gpu/drm/udl/udl_connector.c @@ -17,18 +17,19 @@ #include "udl_connector.h" #include "udl_drv.h" -static bool udl_get_edid_block(struct udl_device *udl, int block_idx, - u8 *buff) +static int udl_get_edid_block(void *data, u8 *buf, unsigned int block, + size_t len) { int ret, i; u8 *read_buff; + struct udl_device *udl = data; read_buff = kmalloc(2, GFP_KERNEL); if (!read_buff) - return false; + return -1; - for (i = 0; i < EDID_LENGTH; i++) { - int bval = (i + block_idx * EDID_LENGTH) << 8; + for (i = 0; i < len; i++) { + int bval = (i + block * EDID_LENGTH) << 8; ret = usb_control_msg(udl->udev, usb_rcvctrlpipe(udl->udev, 0), (0x02), (0x80 | (0x02 << 5)), bval, @@ -36,60 +37,13 @@ static bool udl_get_edid_block(struct udl_device *udl, int block_idx, if (ret < 1) { DRM_ERROR("Read EDID byte %d failed err %x\n", i, ret); kfree(read_buff); - return false; + return -1; } - buff[i] = read_buff[1]; + buf[i] = read_buff[1]; } kfree(read_buff); - return true; -} - -static bool udl_get_edid(struct udl_device *udl, u8 **result_buff, - int *result_buff_size) -{ - int i, extensions; - u8 *block_buff = NULL, *buff_ptr; - - block_buff = kmalloc(EDID_LENGTH, GFP_KERNEL); - if (block_buff == NULL) - return false; - - if (udl_get_edid_block(udl, 0, block_buff) && - memchr_inv(block_buff, 0, EDID_LENGTH)) { - extensions = ((struct edid *)block_buff)->extensions; - if (extensions > 0) { - /* we have to read all extensions one by one */ - *result_buff_size = EDID_LENGTH * (extensions + 1); - *result_buff = kmalloc(*result_buff_size, GFP_KERNEL); - buff_ptr = *result_buff; - if (buff_ptr == NULL) { - kfree(block_buff); - return false; - } - memcpy(buff_ptr, block_buff, EDID_LENGTH); - kfree(block_buff); - buff_ptr += EDID_LENGTH; - for (i = 1; i < extensions; ++i) { - if (udl_get_edid_block(udl, i, buff_ptr)) { - buff_ptr += EDID_LENGTH; - } else { - kfree(*result_buff); - *result_buff = NULL; - return false; - } - } - return true; - } - /* we have only base edid block */ - *result_buff = block_buff; - *result_buff_size = EDID_LENGTH; - return true; - } - - kfree(block_buff); - - return false; + return 0; } static int udl_get_modes(struct drm_connector *connector) @@ -121,8 +75,6 @@ static int udl_mode_valid(struct drm_connector *connector, static enum drm_connector_status udl_detect(struct drm_connector *connector, bool force) { - u8 *edid_buff = NULL; - int edid_buff_size = 0; struct udl_device *udl = connector->dev->dev_private; struct udl_drm_connector *udl_connector = container_of(connector, @@ -135,12 +87,10 @@ udl_detect(struct drm_connector *connector, bool force) udl_connector->edid = NULL; } - - if (!udl_get_edid(udl, &edid_buff, &edid_buff_size)) + udl_connector->edid = drm_do_get_edid(connector, udl_get_edid_block, udl); + if (!udl_connector->edid) return connector_status_disconnected; - udl_connector->edid = (struct edid *)edid_buff; - return connector_status_connected; }