Perhaps too many developers do not know that using '%#<width>x'
in printf output _includes_ the 0x prefix in the output width.
So %#02x already has the width taken by the 0x prefix and will
always emit 3 or more output bytes.
sprintf(buf, "%#02x", 1) emits 0x1 (3 bytes of output)
sprintf(buf, "%#02x", 255) emits 0xff (4 bytes of output)
So presumably all the uses of %#02x in the kernel are not outputting
what is actually expected. Perhaps all of these should use %#04x.
Instances of the nominally defective '%#02x' from today's -next are:
$ git grep -i '%#02x'
arch/arc/kernel/setup.c: "\nIDENTITY\t: ARCVER [%#02x] ARCNUM [%#02x] CHIPID [%#4x]\n",
drivers/gpu/drm/bridge/analogix/analogix-anx6345.c: DRM_DEBUG_KMS("DP bandwidth (%#02x) not supported\n", dp_bw);
drivers/gpu/drm/bridge/analogix/analogix-anx78xx.c: DRM_DEBUG_KMS("DP bandwidth (%#02x) not supported\n", dp_bw);
drivers/gpu/drm/drm_hdcp.c: DRM_DEBUG("\t%#02x, %#02x, %#02x, %#02x, %#02x\n",
drivers/gpu/drm/omapdrm/dss/dsi.c: DSSDBG("\t\tb1 %#02x b2 %#02x b3 %#02x b4 %#02x\n",
drivers/gpu/drm/rockchip/rockchip_drm_vop.c: DRM_DEV_ERROR(vop->dev, "Unknown VOP IRQs: %#02x\n",
drivers/hid/hid-ft260.c: ft260_dbg("bus_status %#02x, clock %u\n", report.bus_status,
drivers/hid/hid-ft260.c: ft260_dbg("rep %#02x addr %#02x off %d len %d d[0] %#02x\n",
drivers/hid/hid-ft260.c: ft260_dbg("rep %#02x addr %#02x cmd %#02x datlen %d replen %d\n",
drivers/hid/hid-ft260.c: ft260_dbg("rep %#02x addr %#02x len %d\n", rep.report, rep.address,
drivers/hid/hid-ft260.c: hid_err(hdev, "unknown report: %#02x\n", xfer->report);
drivers/hid/hid-ft260.c: ft260_dbg("i2c resp: rep %#02x len %d\n", xfer->report, xfer->length);
drivers/i2c/algos/i2c-algo-pca.c: printk(KERN_INFO " [%02d] RD %d bytes from %#02x [%#02x, ...]\n",
drivers/i2c/algos/i2c-algo-pca.c: printk(KERN_INFO " [%02d] WR %d bytes to %#02x [%#02x%s",
drivers/iio/imu/inv_icm42600/inv_icm42600_core.c: dev_err(dev, "invalid whoami %#02x expected %#02x (%s)\n",
drivers/input/misc/atmel_captouch.c: "I2C read error: register address does not match (%#02x vs %02x)\n",
drivers/input/misc/atmel_captouch.c: dev_dbg(dev, "%s: button state %#02x\n", __func__, new_btn);
drivers/input/mouse/elantech.c: "failed to read register %#02x\n", reg);
drivers/input/mouse/elantech.c: "failed to write register %#02x with value %#02x%#02x\n",
drivers/input/mouse/elantech.c: "Elan ic body: %#04x, current fw version: %#02x\n",
drivers/input/rmi4/rmi_f01.c: "Device was reset during configuration process, status: %#02x!\n",
drivers/input/rmi4/rmi_f34.c: "%s: Failed to read cmd register: %d (command %#02x)\n",
drivers/input/rmi4/rmi_f34.c: "Failed to write F34 command %#02x: %d\n",
drivers/input/rmi4/rmi_f34.c: "%s: cmd %#02x timed out: %d\n",
drivers/input/rmi4/rmi_f34.c: "%s: cmd %#02x timed out, status: %#02x\n",
drivers/input/rmi4/rmi_f34.c: rmi_dbg(RMI_DEBUG_FN, &fn->dev, "%s: status: %#02x, ret: %d\n",
drivers/input/rmi4/rmi_f34.c: rmi_dbg(RMI_DEBUG_FN, &fn->dev, "%s: status: %#02x, ret: %d\n",
drivers/input/serio/libps2.c: "failed to write %#02x: %d\n", byte, error);
drivers/input/serio/libps2.c: dev_dbg(&ps2dev->serio->dev, "unexpected %#02x\n", data);
drivers/input/touchscreen/ad7879.c: dev_err(ts->dev, "failed to read register %#02x: %d\n",
drivers/input/touchscreen/ad7879.c: "failed to write %#04x to register %#02x: %d\n",
drivers/input/touchscreen/ad7879.c: dev_err_ratelimited(ts->dev, "failed to read %#02x: %d\n",
drivers/input/touchscreen/bu21029_ts.c: "failed to write %#02x to register %#02x: %d\n",
drivers/input/touchscreen/ektf2127.c: dev_err(dev, "Unexpected packet header byte %#02x\n", buf[0]);
drivers/input/touchscreen/ektf2127.c: dev_err(dev, "Unexpected %s data: %#02x %#02x\n",
drivers/input/touchscreen/hideep.c: "%s: mismatch @%#08x: (%#02x vs %#02x)\n",
drivers/input/touchscreen/melfas_mip4.c: "Unexpected bootloader status: %#02x\n",
drivers/input/touchscreen/sis_i2c.c: "%s: invalid packet ID %#02x\n",
drivers/input/touchscreen/sis_i2c.c: dev_err(&ts->client->dev, "Unexpected touch status: %#02x\n",
drivers/input/touchscreen/stmfts.c: "unknown key event: %#02x\n", event[2]);
drivers/input/touchscreen/stmfts.c: "unknown event %#02x\n", event[0]);
drivers/input/touchscreen/stmfts.c: return sprintf(buf, "%#02x\n", status[0]);
drivers/macintosh/adbhid.c: pr_err("ADB HID on ID %d not yet registered, packet %#02x, %#02x, %#02x, %#02x\n",
drivers/macintosh/adbhid.c: pr_info("Unhandled ADB key (scancode %#02x) %s.\n", keycode,
drivers/mtd/chips/cfi_cmdset_0002.c: "version %c.%c (%#02x/%#02x).\n",
drivers/mtd/nand/raw/brcmnand/brcmnand.c: "timeout waiting for command %#02x\n", cmd);
drivers/net/ethernet/amd/ariadne.c: netdev_dbg(dev, "interrupt csr0=%#02x new csr=%#02x [",
drivers/net/ethernet/dec/tulip/timer.c: netdev_dbg(dev, "Transceiver monitor tick CSR12=%#02x, no media sense\n",
drivers/net/ethernet/dec/tulip/timer.c: netdev_dbg(dev, "Transceiver monitor tick: CSR12=%#02x bit %d is %d, expecting %d\n",
drivers/net/ethernet/netronome/nfp/bpf/verifier.c: pr_vlog(env, "instruction %#02x not supported\n",
drivers/net/ethernet/xircom/xirc2ps_cs.c: pr_debug("rsr=%#02x packet_length=%u\n", rsr, pktlen);
drivers/net/ethernet/xircom/xirc2ps_cs.c: pr_debug("rsr=%#02x\n", rsr);
drivers/net/ethernet/xircom/xirc2ps_cs.c: pr_debug("%s: ESR is: %#02x\n", dev->name, value);
drivers/net/ethernet/xircom/xirc2ps_cs.c: pr_debug("%s: ECR is: %#02x\n", dev->name, value);
drivers/pci/controller/pcie-iproc.c: dev_err(dev, "in EP mode, hdr=%#02x\n", hdr_type);
drivers/pci/pci.c: pci_info(dev, "BAR %d: %pR (from Enhanced Allocation, properties %#02x)\n",
drivers/pci/pci.c: pci_info(dev, "ROM: %pR (from Enhanced Allocation, properties %#02x)\n",
drivers/pci/pci.c: pci_info(dev, "VF BAR %d: %pR (from Enhanced Allocation, properties %#02x)\n",
drivers/pci/pci.c: pci_info(dev, "BEI %d res: %pR (from Enhanced Allocation, properties %#02x)\n",
drivers/pci/probe.c: dev_dbg(&bus->dev, "%pR extended by %#02x\n",
drivers/pnp/quirks.c: "from %#02x to 0x0A (1, 3)\n",
drivers/s390/cio/qdio_main.c: DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "in nop:%1d %#02x",
drivers/scsi/aic7xxx/aic79xx_core.c: printk("%#02x", hscb->shared_data.idata.cdb[i]);
drivers/scsi/aic7xxx/aic7xxx_core.c: printk("%#02x", hscb->shared_data.cdb[i]);
drivers/scsi/ibmvscsi/ibmvscsi.c: "bad SRP RSP type %#02x\n", rsp->opcode);
drivers/scsi/qla2xxx/qla_init.c: "%s %s: mask=%#02x gen=%#04x ver=%u.%u map=%#01x sum=%#08x sig=%#08x\n",
drivers/scsi/virtio_scsi.c: "cmd %p response %u status %#02x sense_len %u\n",
drivers/scsi/virtio_scsi.c: "cmd %p CDB: %#02x\n", sc, sc->cmnd[0]);
drivers/soc/qcom/cpr.c: dev_dbg(drv->dev, "IRQ_STATUS = %#02x\n", val);
drivers/soc/qcom/cpr.c: "Interrupt broken? RBCPR_CTL = %#02x\n",
drivers/soc/qcom/cpr.c: seq_printf(s, "rbcpr_gcnt_target (%u) = %#02X\n", ro_sel, gcnt);
drivers/soc/qcom/cpr.c: seq_printf(s, "rbcpr_ctl = %#02X\n", ctl);
drivers/soc/qcom/cpr.c: seq_printf(s, "rbcpr_irq_status = %#02X\n", irq_status);
drivers/soc/qcom/cpr.c: seq_printf(s, "rbcpr_result_0 = %#02X\n", reg);
drivers/staging/wfx/fwio.c: dev_info(wdev->dev, "secure boot: Error %#02x\n", reg);
drivers/target/target_core_transport.c: pr_debug("%scmd %#02x:%#02x with tag %#llx dir %s i_state %d t_state %s len %d refcnt %d transport_state %s\n",
drivers/vhost/scsi.c: pr_debug("%s tv_cmd %p resid %u status %#02x\n", __func__,
drivers/vhost/scsi.c: pr_debug("vhost_scsi got command opcode: %#02x, lun: %d\n",
drivers/video/fbdev/omap2/omapfb/dss/dsi.c: DSSDBG("\t\tb1 %#02x b2 %#02x b3 %#02x b4 %#02x\n",
fs/jffs2/debug.c: printk(JFFS2_DBG "compr:\t%#02x\n", node.i.compr);
fs/jffs2/debug.c: printk(JFFS2_DBG "usercompr:\t%#02x\n", node.i.usercompr);
fs/jffs2/debug.c: printk(JFFS2_DBG "nsize:\t%#02x\n", node.d.nsize);
fs/jffs2/debug.c: printk(JFFS2_DBG "type:\t%#02x\n", node.d.type);
fs/jffs2/readinode.c: JFFS2_ERROR("illegal nsize in node at %#08x: nsize %#02x, totlen %#04x\n",
include/drm/drm_mipi_dbi.h: dev_err_ratelimited(dev, "error %d when sending command %#02x\n", ret, cmd); \
lib/test_printf.c: test("0xfffffff0|0xf0|0xf0", "%#02x|%#02x|%#02x", val, val & 0xff, (u8)val);
net/mac80211/debugfs_sta.c: p += scnprintf(p, sizeof(buf) + buf - p, "next dialog_token: %#02x\n",
sound/soc/codecs/rt5640.c: dev_dbg(component->dev, "detect status %#02x\n", status);
sound/soc/codecs/rt5651.c: dev_dbg(component->dev, "detect report %#02x\n", report);
sound/usb/card.c: "unknown interface protocol %#02x, assuming v1\n",
sound/usb/stream.c: dev_dbg(&dev->dev, "%u:%d: unknown interface protocol %#02x, assuming v1\n",
