Valve for dispensing fluid product and device for dispensing fluid product including such valve

The invention relates to a valve for dispensing a fluid product, that comprises a valve body (10) including a dosage chamber (20) and a valve member (30) sliding in the valve body (10) between a rest position and a dispensing position for selectively dispensing the content of the dosage chamber (20), the dosage chamber (20) being connected, during the rest position of the valve member (30) to a fluid product tank containing the product to be dispensed via a fluid flow passage (35, 35'), the valve member (30) including a radial bearing collar, and the fluid flow passage (35, 35') at the collar(320) extending at least partially inside the valve member (30) and/or the collar (320) for allowing the filling of the dosage chamber (20) by gravity when, in the rest position of the valve member (30), the valve is in an inverted position relative to the dosage chamber (20) provided under the tank, and or allowing the emptying of the dosage chamber (20) by gravity when, in the rest position of the valve member (30), the