Re: [PATCH v5 2/8] usb: pd: Update VDO definitions

From: Heikki Krogerus
Date: Wed Feb 03 2021 - 07:55:14 EST

Next message: Daniel Axtens: "Re: [PATCH v10 6/6] powerpc: Book3S 64-bit outline-only KASAN support"
Previous message: Miklos Szeredi: "[PATCH 12/18] hfsplus: convert to miscattr"
In reply to: Kyle Tso: "[PATCH v5 2/8] usb: pd: Update VDO definitions"
Next in thread: Greg KH: "Re: [PATCH v5 2/8] usb: pd: Update VDO definitions"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

On Wed, Feb 03, 2021 at 12:17:27AM +0800, Kyle Tso wrote:
> "PD Spec Revision 3.0 Version 2.0 + ECNs 2020-12-10" introduces several
> changes regarding the ID Header VDO and the Product Type VDOs.
>
> Signed-off-by: Kyle Tso <kyletso@xxxxxxxxxx>

Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>

> ---
> drivers/usb/typec/class.c | 8 +-
> include/linux/usb/pd_vdo.h | 308 ++++++++++++++++++++++++++++---------
> 2 files changed, 242 insertions(+), 74 deletions(-)
>
> diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> index 42d1be1eece9..1db08138b75d 100644
> --- a/drivers/usb/typec/class.c
> +++ b/drivers/usb/typec/class.c
> @@ -89,7 +89,7 @@ static const char * const typec_accessory_modes[] = {
>
> /* Product types defined in USB PD Specification R3.0 V2.0 */
> static const char * const product_type_ufp[8] = {
> - [IDH_PTYPE_UNDEF] = "undefined",
> + [IDH_PTYPE_NOT_UFP] = "not_ufp",
> [IDH_PTYPE_HUB] = "hub",
> [IDH_PTYPE_PERIPH] = "peripheral",
> [IDH_PTYPE_PSD] = "psd",
> @@ -97,17 +97,17 @@ static const char * const product_type_ufp[8] = {
> };
>
> static const char * const product_type_dfp[8] = {
> - [IDH_PTYPE_DFP_UNDEF] = "undefined",
> + [IDH_PTYPE_NOT_DFP] = "not_dfp",
> [IDH_PTYPE_DFP_HUB] = "hub",
> [IDH_PTYPE_DFP_HOST] = "host",
> [IDH_PTYPE_DFP_PB] = "power_brick",
> - [IDH_PTYPE_DFP_AMC] = "amc",
> };
>
> static const char * const product_type_cable[8] = {
> - [IDH_PTYPE_UNDEF] = "undefined",
> + [IDH_PTYPE_NOT_CABLE] = "not_cable",
> [IDH_PTYPE_PCABLE] = "passive",
> [IDH_PTYPE_ACABLE] = "active",
> + [IDH_PTYPE_VPD] = "vpd",
> };
>
> static struct usb_pd_identity *get_pd_identity(struct device *dev)
> diff --git a/include/linux/usb/pd_vdo.h b/include/linux/usb/pd_vdo.h
> index 8c08eeb9a74b..e9b6822c54c2 100644
> --- a/include/linux/usb/pd_vdo.h
> +++ b/include/linux/usb/pd_vdo.h
> @@ -103,34 +103,46 @@
> * --------------------
> * <31> :: data capable as a USB host
> * <30> :: data capable as a USB device
> - * <29:27> :: product type (UFP / Cable)
> + * <29:27> :: product type (UFP / Cable / VPD)
> * <26> :: modal operation supported (1b == yes)
> - * <25:16> :: product type (DFP)
> + * <25:23> :: product type (DFP) (SVDM version 2.0+ only; set to zero in version 1.0)
> + * <22:21> :: connector type (SVDM version 2.0+ only; set to zero in version 1.0)
> + * <20:16> :: Reserved, Shall be set to zero
> * <15:0> :: USB-IF assigned VID for this cable vendor
> */
> -#define IDH_PTYPE_UNDEF 0
> +/* SOP Product Type (UFP) */
> +#define IDH_PTYPE_NOT_UFP 0
> #define IDH_PTYPE_HUB 1
> #define IDH_PTYPE_PERIPH 2
> #define IDH_PTYPE_PSD 3
> #define IDH_PTYPE_AMA 5
>
> +/* SOP' Product Type (Cable Plug / VPD) */
> +#define IDH_PTYPE_NOT_CABLE 0
> #define IDH_PTYPE_PCABLE 3
> #define IDH_PTYPE_ACABLE 4
> +#define IDH_PTYPE_VPD 6
>
> -#define IDH_PTYPE_DFP_UNDEF 0
> +/* SOP Product Type (DFP) */
> +#define IDH_PTYPE_NOT_DFP 0
> #define IDH_PTYPE_DFP_HUB 1
> #define IDH_PTYPE_DFP_HOST 2
> #define IDH_PTYPE_DFP_PB 3
> -#define IDH_PTYPE_DFP_AMC 4
>
> -#define VDO_IDH(usbh, usbd, ptype, is_modal, vid) \
> - ((usbh) << 31 | (usbd) << 30 | ((ptype) & 0x7) << 27 \
> - | (is_modal) << 26 | ((vid) & 0xffff))
> +/* ID Header Mask */
> +#define IDH_DFP_MASK GENMASK(25, 23)
> +#define IDH_CONN_MASK GENMASK(22, 21)
> +
> +#define VDO_IDH(usbh, usbd, ufp_cable, is_modal, dfp, conn, vid) \
> + ((usbh) << 31 | (usbd) << 30 | ((ufp_cable) & 0x7) << 27 \
> + | (is_modal) << 26 | ((dfp) & 0x7) << 23 | ((conn) & 0x3) << 21 \
> + | ((vid) & 0xffff))
>
> #define PD_IDH_PTYPE(vdo) (((vdo) >> 27) & 0x7)
> #define PD_IDH_VID(vdo) ((vdo) & 0xffff)
> #define PD_IDH_MODAL_SUPP(vdo) ((vdo) & (1 << 26))
> #define PD_IDH_DFP_PTYPE(vdo) (((vdo) >> 23) & 0x7)
> +#define PD_IDH_CONN_TYPE(vdo) (((vdo) >> 21) & 0x3)
>
> /*
> * Cert Stat VDO
> @@ -138,6 +150,7 @@
> * <31:0> : USB-IF assigned XID for this cable
> */
> #define PD_CSTAT_XID(vdo) (vdo)
> +#define VDO_CERT(xid) ((xid) & 0xffffffff)
>
> /*
> * Product VDO
> @@ -149,112 +162,267 @@
> #define PD_PRODUCT_PID(vdo) (((vdo) >> 16) & 0xffff)
>
> /*
> - * UFP VDO1
> + * UFP VDO (PD Revision 3.0+ only)
> * --------
> * <31:29> :: UFP VDO version
> * <28> :: Reserved
> * <27:24> :: Device capability
> - * <23:6> :: Reserved
> + * <23:22> :: Connector type (10b == receptacle, 11b == captive plug)
> + * <21:11> :: Reserved
> + * <10:8> :: Vconn power (AMA only)
> + * <7> :: Vconn required (AMA only, 0b == no, 1b == yes)
> + * <6> :: Vbus required (AMA only, 0b == yes, 1b == no)
> * <5:3> :: Alternate modes
> * <2:0> :: USB highest speed
> */
> -#define PD_VDO1_UFP_DEVCAP(vdo) (((vdo) & GENMASK(27, 24)) >> 24)
> +#define PD_VDO_UFP_DEVCAP(vdo) (((vdo) & GENMASK(27, 24)) >> 24)
> +
> +/* UFP VDO Version */
> +#define UFP_VDO_VER1_2 2
>
> +/* Device Capability */
> #define DEV_USB2_CAPABLE BIT(0)
> #define DEV_USB2_BILLBOARD BIT(1)
> #define DEV_USB3_CAPABLE BIT(2)
> #define DEV_USB4_CAPABLE BIT(3)
>
> +/* Connector Type */
> +#define UFP_RECEPTACLE 2
> +#define UFP_CAPTIVE 3
> +
> +/* Vconn Power (AMA only, set to AMA_VCONN_NOT_REQ if Vconn is not required) */
> +#define AMA_VCONN_PWR_1W 0
> +#define AMA_VCONN_PWR_1W5 1
> +#define AMA_VCONN_PWR_2W 2
> +#define AMA_VCONN_PWR_3W 3
> +#define AMA_VCONN_PWR_4W 4
> +#define AMA_VCONN_PWR_5W 5
> +#define AMA_VCONN_PWR_6W 6
> +
> +/* Vconn Required (AMA only) */
> +#define AMA_VCONN_NOT_REQ 0
> +#define AMA_VCONN_REQ 1
> +
> +/* Vbus Required (AMA only) */
> +#define AMA_VBUS_REQ 0
> +#define AMA_VBUS_NOT_REQ 1
> +
> +/* Alternate Modes */
> +#define UFP_ALTMODE_NOT_SUPP 0
> +#define UFP_ALTMODE_TBT3 BIT(0)
> +#define UFP_ALTMODE_RECFG BIT(1)
> +#define UFP_ALTMODE_NO_RECFG BIT(2)
> +
> +/* USB Highest Speed */
> +#define UFP_USB2_ONLY 0
> +#define UFP_USB32_GEN1 1
> +#define UFP_USB32_4_GEN2 2
> +#define UFP_USB4_GEN3 3
> +
> +#define VDO_UFP(ver, cap, conn, vcpwr, vcr, vbr, alt, spd) \
> + (((ver) & 0x7) << 29 | ((cap) & 0xf) << 24 | ((conn) & 0x3) << 22 \
> + | ((vcpwr) & 0x7) << 8 | (vcr) << 7 | (vbr) << 6 | ((alt) & 0x7) << 3 \
> + | ((spd) & 0x7))
> +
> /*
> - * DFP VDO
> + * DFP VDO (PD Revision 3.0+ only)
> * --------
> * <31:29> :: DFP VDO version
> * <28:27> :: Reserved
> * <26:24> :: Host capability
> - * <23:5> :: Reserved
> + * <23:22> :: Connector type (10b == receptacle, 11b == captive plug)
> + * <21:5> :: Reserved
> * <4:0> :: Port number
> */
> #define PD_VDO_DFP_HOSTCAP(vdo) (((vdo) & GENMASK(26, 24)) >> 24)
>
> +#define DFP_VDO_VER1_1 1
> #define HOST_USB2_CAPABLE BIT(0)
> #define HOST_USB3_CAPABLE BIT(1)
> #define HOST_USB4_CAPABLE BIT(2)
> +#define DFP_RECEPTACLE 2
> +#define DFP_CAPTIVE 3
> +
> +#define VDO_DFP(ver, cap, conn, pnum) \
> + (((ver) & 0x7) << 29 | ((cap) & 0x7) << 24 | ((conn) & 0x3) << 22 \
> + | ((pnum) & 0x1f))
>
> /*
> - * Cable VDO
> + * Passive Cable VDO
> * ---------
> * <31:28> :: Cable HW version
> * <27:24> :: Cable FW version
> - * <23:20> :: Reserved, Shall be set to zero
> - * <19:18> :: type-C to Type-A/B/C/Captive (00b == A, 01 == B, 10 == C, 11 == Captive)
> - * <17> :: Type-C to Plug/Receptacle (0b == plug, 1b == receptacle)
> + * <23:21> :: VDO version
> + * <20> :: Reserved, Shall be set to zero
> + * <19:18> :: Type-C to Type-C/Captive (10b == C, 11b == Captive)
> + * <17> :: Reserved, Shall be set to zero
> * <16:13> :: cable latency (0001 == <10ns(~1m length))
> - * <12:11> :: cable termination type (11b == both ends active VCONN req)
> - * <10> :: SSTX1 Directionality support (0b == fixed, 1b == cfgable)
> - * <9> :: SSTX2 Directionality support
> - * <8> :: SSRX1 Directionality support
> - * <7> :: SSRX2 Directionality support
> - * <6:5> :: Vbus current handling capability
> + * <12:11> :: cable termination type (10b == Vconn not req, 01b == Vconn req)
> + * <10:9> :: Maximum Vbus voltage (00b == 20V, 01b == 30V, 10b == 40V, 11b == 50V)
> + * <8:7> :: Reserved, Shall be set to zero
> + * <6:5> :: Vbus current handling capability (01b == 3A, 10b == 5A)
> + * <4:3> :: Reserved, Shall be set to zero
> + * <2:0> :: USB highest speed
> + *
> + * Active Cable VDO 1
> + * ---------
> + * <31:28> :: Cable HW version
> + * <27:24> :: Cable FW version
> + * <23:21> :: VDO version
> + * <20> :: Reserved, Shall be set to zero
> + * <19:18> :: Connector type (10b == C, 11b == Captive)
> + * <17> :: Reserved, Shall be set to zero
> + * <16:13> :: cable latency (0001 == <10ns(~1m length))
> + * <12:11> :: cable termination type (10b == one end active, 11b == both ends active VCONN req)
> + * <10:9> :: Maximum Vbus voltage (00b == 20V, 01b == 30V, 10b == 40V, 11b == 50V)
> + * <8> :: SBU supported (0b == supported, 1b == not supported)
> + * <7> :: SBU type (0b == passive, 1b == active)
> + * <6:5> :: Vbus current handling capability (01b == 3A, 10b == 5A)
> * <4> :: Vbus through cable (0b == no, 1b == yes)
> * <3> :: SOP" controller present? (0b == no, 1b == yes)
> - * <2:0> :: USB SS Signaling support
> + * <2:0> :: USB highest speed
> */
> -#define CABLE_ATYPE 0
> -#define CABLE_BTYPE 1
> +/* Cable VDO Version */
> +#define CABLE_VDO_VER1_0 0
> +#define CABLE_VDO_VER1_3 3
> +
> +/* Connector Type */
> #define CABLE_CTYPE 2
> #define CABLE_CAPTIVE 3
> -#define CABLE_PLUG 0
> -#define CABLE_RECEPTACLE 1
> -#define CABLE_CURR_1A5 0
> +
> +/* Cable Latency */
> +#define CABLE_LATENCY_1M 1
> +#define CABLE_LATENCY_2M 2
> +#define CABLE_LATENCY_3M 3
> +#define CABLE_LATENCY_4M 4
> +#define CABLE_LATENCY_5M 5
> +#define CABLE_LATENCY_6M 6
> +#define CABLE_LATENCY_7M 7
> +#define CABLE_LATENCY_7M_PLUS 8
> +
> +/* Cable Termination Type */
> +#define PCABLE_VCONN_NOT_REQ 0
> +#define PCABLE_VCONN_REQ 1
> +#define ACABLE_ONE_END 2
> +#define ACABLE_BOTH_END 3
> +
> +/* Maximum Vbus Voltage */
> +#define CABLE_MAX_VBUS_20V 0
> +#define CABLE_MAX_VBUS_30V 1
> +#define CABLE_MAX_VBUS_40V 2
> +#define CABLE_MAX_VBUS_50V 3
> +
> +/* Active Cable SBU Supported/Type */
> +#define ACABLE_SBU_SUPP 0
> +#define ACABLE_SBU_NOT_SUPP 1
> +#define ACABLE_SBU_PASSIVE 0
> +#define ACABLE_SBU_ACTIVE 1
> +
> +/* Vbus Current Handling Capability */
> +#define CABLE_CURR_DEF 0
> #define CABLE_CURR_3A 1
> #define CABLE_CURR_5A 2
> -#define CABLE_USBSS_U2_ONLY 0
> -#define CABLE_USBSS_U31_GEN1 1
> -#define CABLE_USBSS_U31_GEN2 2
> -#define VDO_CABLE(hw, fw, cbl, gdr, lat, term, tx1d, tx2d, rx1d, rx2d, cur,\
> - vps, sopp, usbss) \
> - (((hw) & 0x7) << 28 | ((fw) & 0x7) << 24 | ((cbl) & 0x3) << 18 \
> - | (gdr) << 17 | ((lat) & 0x7) << 13 | ((term) & 0x3) << 11 \
> - | (tx1d) << 10 | (tx2d) << 9 | (rx1d) << 8 | (rx2d) << 7 \
> - | ((cur) & 0x3) << 5 | (vps) << 4 | (sopp) << 3 \
> - | ((usbss) & 0x7))
> +
> +/* USB Highest Speed */
> +#define CABLE_USB2_ONLY 0
> +#define CABLE_USB32_GEN1 1
> +#define CABLE_USB32_4_GEN2 2
> +#define CABLE_USB4_GEN3 3
> +
> +#define VDO_PCABLE(hw, fw, ver, conn, lat, term, vbm, cur, spd) \
> + (((hw) & 0xf) << 28 | ((fw) & 0xf) << 24 | ((ver) & 0x7) << 21 \
> + | ((conn) & 0x3) << 18 | ((lat) & 0xf) << 13 | ((term) & 0x3) << 11 \
> + | ((vbm) & 0x3) << 9 | ((cur) & 0x3) << 5 | ((spd) & 0x7))
> +#define VDO_ACABLE1(hw, fw, ver, conn, lat, term, vbm, sbu, sbut, cur, vbt, sopp, spd) \
> + (((hw) & 0xf) << 28 | ((fw) & 0xf) << 24 | ((ver) & 0x7) << 21 \
> + | ((conn) & 0x3) << 18 | ((lat) & 0xf) << 13 | ((term) & 0x3) << 11 \
> + | ((vbm) & 0x3) << 9 | (sbu) << 8 | (sbut) << 7 | ((cur) & 0x3) << 5 \
> + | (vbt) << 4 | (sopp) << 3 | ((spd) & 0x7))
> +
> #define VDO_TYPEC_CABLE_TYPE(vdo) (((vdo) >> 18) & 0x3)
>
> /*
> - * AMA VDO
> + * Active Cable VDO 2
> * ---------
> - * <31:28> :: Cable HW version
> - * <27:24> :: Cable FW version
> - * <23:12> :: Reserved, Shall be set to zero
> - * <11> :: SSTX1 Directionality support (0b == fixed, 1b == cfgable)
> - * <10> :: SSTX2 Directionality support
> - * <9> :: SSRX1 Directionality support
> - * <8> :: SSRX2 Directionality support
> - * <7:5> :: Vconn power
> - * <4> :: Vconn power required
> - * <3> :: Vbus power required
> - * <2:0> :: USB SS Signaling support
> + * <31:24> :: Maximum operating temperature
> + * <23:16> :: Shutdown temperature
> + * <15> :: Reserved, Shall be set to zero
> + * <14:12> :: U3/CLd power
> + * <11> :: U3 to U0 transition mode (0b == direct, 1b == through U3S)
> + * <10> :: Physical connection (0b == copper, 1b == optical)
> + * <9> :: Active element (0b == redriver, 1b == retimer)
> + * <8> :: USB4 supported (0b == yes, 1b == no)
> + * <7:6> :: USB2 hub hops consumed
> + * <5> :: USB2 supported (0b == yes, 1b == no)
> + * <4> :: USB3.2 supported (0b == yes, 1b == no)
> + * <3> :: USB lanes supported (0b == one lane, 1b == two lanes)
> + * <2> :: Optically isolated active cable (0b == no, 1b == yes)
> + * <1> :: Reserved, Shall be set to zero
> + * <0> :: USB gen (0b == gen1, 1b == gen2+)
> */
> -#define VDO_AMA(hw, fw, tx1d, tx2d, rx1d, rx2d, vcpwr, vcr, vbr, usbss) \
> - (((hw) & 0x7) << 28 | ((fw) & 0x7) << 24 \
> - | (tx1d) << 11 | (tx2d) << 10 | (rx1d) << 9 | (rx2d) << 8 \
> - | ((vcpwr) & 0x7) << 5 | (vcr) << 4 | (vbr) << 3 \
> - | ((usbss) & 0x7))
> -
> -#define PD_VDO_AMA_VCONN_REQ(vdo) (((vdo) >> 4) & 1)
> -#define PD_VDO_AMA_VBUS_REQ(vdo) (((vdo) >> 3) & 1)
> +/* U3/CLd Power*/
> +#define ACAB2_U3_CLD_10MW_PLUS 0
> +#define ACAB2_U3_CLD_10MW 1
> +#define ACAB2_U3_CLD_5MW 2
> +#define ACAB2_U3_CLD_1MW 3
> +#define ACAB2_U3_CLD_500UW 4
> +#define ACAB2_U3_CLD_200UW 5
> +#define ACAB2_U3_CLD_50UW 6
> +
> +/* Other Active Cable VDO 2 Fields */
> +#define ACAB2_U3U0_DIRECT 0
> +#define ACAB2_U3U0_U3S 1
> +#define ACAB2_PHY_COPPER 0
> +#define ACAB2_PHY_OPTICAL 1
> +#define ACAB2_REDRIVER 0
> +#define ACAB2_RETIMER 1
> +#define ACAB2_USB4_SUPP 0
> +#define ACAB2_USB4_NOT_SUPP 1
> +#define ACAB2_USB2_SUPP 0
> +#define ACAB2_USB2_NOT_SUPP 1
> +#define ACAB2_USB32_SUPP 0
> +#define ACAB2_USB32_NOT_SUPP 1
> +#define ACAB2_LANES_ONE 0
> +#define ACAB2_LANES_TWO 1
> +#define ACAB2_OPT_ISO_NO 0
> +#define ACAB2_OPT_ISO_YES 1
> +#define ACAB2_GEN_1 0
> +#define ACAB2_GEN_2_PLUS 1
> +
> +#define VDO_ACABLE2(mtemp, stemp, u3p, trans, phy, ele, u4, hops, u2, u32, lane, iso, gen) \
> + (((mtemp) & 0xff) << 24 | ((stemp) & 0xff) << 16 | ((u3p) & 0x7) << 12 \
> + | (trans) << 11 | (phy) << 10 | (ele) << 9 | (u4) << 8 \
> + | ((hops) & 0x3) << 6 | (u2) << 5 | (u32) << 4 | (lane) << 3 \
> + | (iso) << 2 | (gen))
>
> -#define AMA_VCONN_PWR_1W 0
> -#define AMA_VCONN_PWR_1W5 1
> -#define AMA_VCONN_PWR_2W 2
> -#define AMA_VCONN_PWR_3W 3
> -#define AMA_VCONN_PWR_4W 4
> -#define AMA_VCONN_PWR_5W 5
> -#define AMA_VCONN_PWR_6W 6
> -#define AMA_USBSS_U2_ONLY 0
> -#define AMA_USBSS_U31_GEN1 1
> -#define AMA_USBSS_U31_GEN2 2
> -#define AMA_USBSS_BBONLY 3
> +/*
> + * VPD VDO
> + * ---------
> + * <31:28> :: HW version
> + * <27:24> :: FW version
> + * <23:21> :: VDO version
> + * <20:17> :: Reserved, Shall be set to zero
> + * <16:15> :: Maximum Vbus voltage (00b == 20V, 01b == 30V, 10b == 40V, 11b == 50V)
> + * <14> :: Charge through current support (0b == 3A, 1b == 5A)
> + * <13> :: Reserved, Shall be set to zero
> + * <12:7> :: Vbus impedance
> + * <6:1> :: Ground impedance
> + * <0> :: Charge through support (0b == no, 1b == yes)
> + */
> +#define VPD_VDO_VER1_0 0
> +#define VPD_MAX_VBUS_20V 0
> +#define VPD_MAX_VBUS_30V 1
> +#define VPD_MAX_VBUS_40V 2
> +#define VPD_MAX_VBUS_50V 3
> +#define VPDCT_CURR_3A 0
> +#define VPDCT_CURR_5A 1
> +#define VPDCT_NOT_SUPP 0
> +#define VPDCT_SUPP 1
> +
> +#define VDO_VPD(hw, fw, ver, vbm, curr, vbi, gi, ct) \
> + (((hw) & 0xf) << 28 | ((fw) & 0xf) << 24 | ((ver) & 0x7) << 21 \
> + | ((vbm) & 0x3) << 15 | (curr) << 14 | ((vbi) & 0x3f) << 7 \
> + | ((gi) & 0x3f) << 1 | (ct))
>
> /*
> * SVDM Discover SVIDs request -> response
> --
> 2.30.0.365.g02bc693789-goog

thanks,

--
heikki

Next message: Daniel Axtens: "Re: [PATCH v10 6/6] powerpc: Book3S 64-bit outline-only KASAN support"
Previous message: Miklos Szeredi: "[PATCH 12/18] hfsplus: convert to miscattr"
In reply to: Kyle Tso: "[PATCH v5 2/8] usb: pd: Update VDO definitions"
Next in thread: Greg KH: "Re: [PATCH v5 2/8] usb: pd: Update VDO definitions"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]