On Thu, Apr 18, 2024 at 08:18:33AM +0200, Greg Kroah-Hartman wrote: > On Wed, Apr 17, 2024 at 07:37:36PM +0200, Alexey Gladkov wrote: > > Each driver has its own restrictions on font size. There is currently no > > way to understand what the requirements are. The new ioctl allows > > userspace to get the minimum and maximum font size values. > > Is there any userspace code that uses this yet that we can point to > here? Yes. I have a code that uses this. It waits for this ioctl to appear in the kernel. https://git.kernel.org/pub/scm/linux/kernel/git/legion/kbd.git/commit/?h=kdfontinfo-v1&id=e2ad0117ca8e46cedd8668934db7b04e9054d5d7 > I know tty ioctls are woefully undocumented, but could there be some > documentation here? Yes, this is a big problem for this interface. The ioctl_console(2) describes PIO_FONT/PIO_FONTX, which is no longer supported, but does not describe KDFONTOP at all, which is exactly used by userspace. My TODO has a task to fix this. But I would suggest creating documentation in the kernel because life shows that man-page is far behind what is implemented. > > > > Acked-by: Helge Deller <deller@xxxxxx> > > Signed-off-by: Alexey Gladkov <legion@xxxxxxxxxx> > > --- > > drivers/tty/vt/vt.c | 24 ++++++++++++++++++++++++ > > drivers/tty/vt/vt_ioctl.c | 13 +++++++++++++ > > include/linux/console.h | 3 +++ > > include/linux/vt_kern.h | 1 + > > include/uapi/linux/kd.h | 14 ++++++++++++++ > > 5 files changed, 55 insertions(+) > > > > diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c > > index 9b5b98dfc8b4..e8db0e9ea674 100644 > > --- a/drivers/tty/vt/vt.c > > +++ b/drivers/tty/vt/vt.c > > @@ -4851,6 +4851,30 @@ int con_font_op(struct vc_data *vc, struct console_font_op *op) > > return -ENOSYS; > > } > > > > +int con_font_info(struct vc_data *vc, struct console_font_info *info) > > +{ > > + int rc; > > + > > + info->min_height = 0; > > + info->max_height = max_font_height; > > + > > + info->min_width = 0; > > + info->max_width = max_font_width; > > + > > + info->flags = KD_FONT_INFO_FLAG_LOW_SIZE | KD_FONT_INFO_FLAG_HIGH_SIZE; > > + > > + console_lock(); > > + if (vc->vc_mode != KD_TEXT) > > + rc = -EINVAL; > > + else if (vc->vc_sw->con_font_info) > > + rc = vc->vc_sw->con_font_info(vc, info); > > + else > > + rc = -ENOSYS; > > + console_unlock(); > > + > > + return rc; > > +} > > + > > /* > > * Interface exported to selection and vcs. > > */ > > diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c > > index 4b91072f3a4e..9a2f8081f650 100644 > > --- a/drivers/tty/vt/vt_ioctl.c > > +++ b/drivers/tty/vt/vt_ioctl.c > > @@ -479,6 +479,19 @@ static int vt_k_ioctl(struct tty_struct *tty, unsigned int cmd, > > break; > > } > > > > + case KDFONTINFO: { > > + struct console_font_info fnt_info; > > + > > + memset(&fnt_info, 0, sizeof(fnt_info)); > > + > > + ret = con_font_info(vc, &fnt_info); > > Shouldn't con_font_info() memset it first? No need to do it in the > caller. > > > + if (ret) > > + return ret; > > + if (copy_to_user(up, &fnt_info, sizeof(fnt_info))) > > + return -EFAULT; > > + break; > > + } > > + > > default: > > return -ENOIOCTLCMD; > > } > > diff --git a/include/linux/console.h b/include/linux/console.h > > index 31a8f5b85f5d..4b798322aa01 100644 > > --- a/include/linux/console.h > > +++ b/include/linux/console.h > > @@ -21,6 +21,7 @@ > > #include <linux/vesa.h> > > > > struct vc_data; > > +struct console_font_info; > > struct console_font_op; > > struct console_font; > > struct module; > > @@ -102,6 +103,8 @@ struct consw { > > bool (*con_switch)(struct vc_data *vc); > > bool (*con_blank)(struct vc_data *vc, enum vesa_blank_mode blank, > > bool mode_switch); > > + int (*con_font_info)(struct vc_data *vc, > > + struct console_font_info *info); > > To make the names more obvious, how about: > con_font_info_get()? > > > int (*con_font_set)(struct vc_data *vc, > > const struct console_font *font, > > unsigned int vpitch, unsigned int flags); > > diff --git a/include/linux/vt_kern.h b/include/linux/vt_kern.h > > index d008c3d0a9bb..383b3a4f6113 100644 > > --- a/include/linux/vt_kern.h > > +++ b/include/linux/vt_kern.h > > @@ -33,6 +33,7 @@ void do_blank_screen(int entering_gfx); > > void do_unblank_screen(int leaving_gfx); > > void poke_blanked_console(void); > > int con_font_op(struct vc_data *vc, struct console_font_op *op); > > +int con_font_info(struct vc_data *vc, struct console_font_info *info); > > int con_set_cmap(unsigned char __user *cmap); > > int con_get_cmap(unsigned char __user *cmap); > > void scrollback(struct vc_data *vc); > > diff --git a/include/uapi/linux/kd.h b/include/uapi/linux/kd.h > > index 8ddb2219a84b..68b715ad4d5c 100644 > > --- a/include/uapi/linux/kd.h > > +++ b/include/uapi/linux/kd.h > > @@ -185,6 +185,20 @@ struct console_font { > > > > #define KD_FONT_FLAG_DONT_RECALC 1 /* Don't recalculate hw charcell size [compat] */ > > > > +/* font information */ > > + > > +#define KD_FONT_INFO_FLAG_LOW_SIZE _BITUL(0) /* 256 */ > > +#define KD_FONT_INFO_FLAG_HIGH_SIZE _BITUL(1) /* 512 */ > > I don't understand why bit 0 and bit 1 have those comments after them. > That's confusing (i.e. bit 0 is NOT 256...) > > > + > > +struct console_font_info { > > + __u32 flags; /* KD_FONT_INFO_FLAG_* */ > > Why are there flags if you are only setting these 2 values? What are > the flags for? > > If this is going to be a "multiplexed" type of structure, then make it a > union? Or maybe we are totally over thinking this whole thing. > > All you want is the min/max font size of the console, right? So perhaps > the whole structure is just: > > > + __u32 min_width, min_height; /* minimal font size */ > > + __u32 max_width, max_height; /* maximum font size */ > > Those 4 variables? Why have anything else here at all? For any new > thing you wish to discover, have it be a new ioctl? > > > + __u32 reserved[5]; /* This field is reserved for future use. Must be 0. */ > > I understand the "must be 0" but this is a read-only structure, so > saying "it will be set to 0" might be better?" Or something like that? > > > +}; > > + > > +#define KDFONTINFO _IOR(KD_IOCTL_BASE, 0x73, struct console_font_info) > > As mentioned above how about KDFONTINFOGET? > > thanks, > > greg k-h > -- Rgrds, legion
